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  • Articles  (186)
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  • Escherichia coli
  • 1990-1994  (186)
  • 1945-1949
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  • Articles  (186)
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  • 1
    Electronic Resource
    Electronic Resource
    HPLC separation of enterobactin and linear 2,3-dihydroxybenzoylserine derivatives: a study on mutants ofEscherichia coli defective in regulation (fur), esterase (fes) and transport (fepA) (1994)
    Springer
    BioMetals 7 (1994), S. 149-154 
    Details
    ISSN: 1572-8773
    Keywords: 2,3-dihydroxybenzoylserine ; enterobactin ; Escherichia coli ; HPLC
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Reversed-phase HPLC separation of enterobactin and its 2,3-dihydroxybenzoylserine derivatives was used for a comparative analysis of mutants of Escherichia coli, defective in the regulation of enterobactin biosynthesis (fur), enterobactin transport (fepA) and enterobactin esterase (fes). A complete separation of all 2,3-dihydroxybenzoylserine compounds was achieved: the monomer (DHBS), the linear dimer (DHBS)2 and trimer (DHBS)3, the cyclic trimer, enterobactin, as well as 2,3-dihydroxybenzoic acid. The production of all these compounds was followed after ethylacetate extraction from acidified culture fluids. Enterobactin was found to be the predominant product in all mutant strains. The mutant strains behaved differently with regard to the breakdown products. All degradation products, such as DHBS, (DHBS)2 and (DHBS)3, were detected in the overproducing fur mutant where both transport and esterase are still functioning, while only the monomer, DHBS, was detected in the fepA mutant and no degradation was found in the esterase-deficient fes mutant. From the pattern of breakdown products it may be inferred that the esterase acts in two different ways, depending on whether transport is functioning or not. Thus, esterolytic cleavage of ferric enterobactin after entering the cells results in a mixture of all three hydrolysis products, i.e. DHBS, (DHBS)2 and (DHBS)3, while cleavage of iron-free enterobactin subsequent to its biosynthesis yields only the monomer. Thus, the results of quantitative HPLC analysis of enterobactin and its breakdown products show that different enterobactin esterase products arise, depending on whether iron is bound to enterobactin or not.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00140485
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  • 2
    Electronic Resource
    Electronic Resource
    Effect of complex nitrogen source on the synthesis and accumulation of poly(3-hydroxybutyric acid) by recombinantEscherichia coli in flask and fed-batch cultures (1994)
    Springer
    Journal of polymers and the environment 2 (1994), S. 169-176 
    Details
    ISSN: 1572-8900
    Keywords: Escherichia coli ; poly(3-hydroxybutyric acid) ; defined medium ; complex nitrogen source ; fed-batch culture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract When a recombinantEscherichia coli XL1-Blue harboring pSYL105 was cultured in a complex medium, a poly(3-hydroxybutyric acid) (PHB) concentration of 7.16 g/L was obtained in 48 h. However, a PHB concentration of only 0.91 g/L was obtained in 60 h by culturing in a defined medium. Also, fed-batch culture in a defined medium resulted in considerably lower PHB accumulation than in a complex medium. With the aim to produce a high concentration of PHB at a reduced medium cost, we examined 10 complex nitrogen sources for their ability to promote PHB synthesis in a defined medium. Tryptone, casamino acids, and casein hydrolysate promoted PHB synthesis to a higher extent than the others tested. PHB synthesis was also enhanced during fedbatch cultures when a defined medium was supplemented with various complex nitrogen sources. With tryptone supplementation a PHB concentration of 66.7 g/L could be obtained in 44 h. Yeast extract was less effective for promoting PHB synthesis than tryptone. Corn steep liquor, which did not enhance PHB synthesis significantly, could promote PHB synthesis considerably when supplemented together with yeast extract in both flask and fed-batch cultures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02067442
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  • 3
    Electronic Resource
    Electronic Resource
    Diversity of siderophore genes encoding biosynthesis of 2,3-dihydroxybenzoic acid in Aeromonas spp. (1994)
    Springer
    BioMetals 7 (1994), S. 227-236 
    Details
    ISSN: 1572-8773
    Keywords: 2,3-dihydroxybenzoic acid ; Aeromonas spp. ; amonabactin ; enterobactin ; Escherichia coli ; iron acquisition ; siderophore genes ; siderophores
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Most species of the genus Aeromonas produce the siderophore amonabactin, although two species produce enterobactin, the siderophore of many enteric bacteria. Both siderophores contain 2,3-dihydroxybenzoic acid (2,3-DHB). Siderophore genes (designated aebC, -E, -B and -A, for aeromonad enterobactin biosynthesis) that complemented mutations in the enterobactin genes of the Escherichia coli 2,3-DHB operon, entCEBA(P15), were cloned from an enterobactin-producing isolate of the Aeromonas spp. Mapping of the aeromonad genes suggested a gene order of aebCEBA, identical to that of the E. coli 2,3-DHB operon. Gene probes for the aeromonad aebCE genes and for amoA (the entC-equivalent gene previously cloned from an amonabactin-producing Aeromonas spp.) did not cross-hybridize. Gene probes for the E. coli 2,3-DHB genes entCEBA did not hybridize with Aeromonas spp. DNA. Therefore, in the genus Aeromonas, 2,3-DHB synthesis is encoded by two distinct gene groups; one (amo) is present in the amonabactin-producers, while the other (aeb) occurs in the enterobactin-producers. Each of these systems differs from (but is functionally related to) the E. coli 2,3-DHB operon. These genes may have diverged from an ancestral group of 2,3-DHB genes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00149553
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  • 4
    Electronic Resource
    Electronic Resource
    Synonymous substitutions are clustered in enterobacterial genes (1994)
    Springer
    Journal of molecular evolution 39 (1994), S. 448-451 
    Details
    ISSN: 1432-1432
    Keywords: Synonymous substitution ; Escherichia coli ; Salmonella typhimurium ; Mutation ; Recombination ; Selection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The spatial distribution of synonymous substitutions in enterobacterial genes is investigated. It is shown that synonymous substitutions are significantly clustered in such a way that a synonymous substitution in one codon elevates the rate of synonymous substitution in an adjacent codon by about 10%. The level of clustering does not appear to be related to the level of gene expression, and it is restricted to a range of two or three codons. There are at least three possible explanations: (1) sequence-directed mutagenesis, (2) recombination, and (3) selection.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00173413
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  • 5
    Electronic Resource
    Electronic Resource
    Hotspots of homologous recombination (1994)
    Springer
    Cellular and molecular life sciences 50 (1994), S. 234-241 
    Details
    ISSN: 1420-9071
    Keywords: Homologous recombination ; hotspots ; nucleases ; meiosis ; Escherichia coli ; Chi ; Schizosaccharomyces pombe ; M26
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Homologous recombination occurs at higher than average frequency at and near hotspots. Hotspots are special nucleotide sequences recognized by proteins that promote, directly or indirectly, a rate limiting step of recombination. This review focuses on two well-studied examples, the Chi sites of the bacteriumEscherichia coli and the M26 site of the fission yeastSchizosaccharomyces pombe. Chi, 5′ G-C-T-G-G-T-G-G 3′, is recognized by the RecBCD enzyme, which nicks the DNA near Chi and produces a 3′-ended single-stranded DNA ‘tail’; this tail is a potent substrate for homologous pairing by RecA and single-stranded DNA binding proteins. M26, 5′ A-T-G-A-C-G-T 3′, is recognized by a heterodimeric protein and stimulates, by an as-yet-unknown mechanism, meiotic recombination at and near theade6 gene. Additional hotspots in bacteria, fungi, and mammals enhance recombination directly or indirectly via a variety of mechanisms. Although hotspots are widespread among organisms, the biological role of their localized enhancement of recombination remains a matter of speculation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01924006
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  • 6
    Electronic Resource
    Electronic Resource
    Sequence divergence of the murB and rrfB genes from Escherichia coli and Salmonella typhimurium (1994)
    Springer
    Archives of microbiology 161 (1994), S. 501-507 
    Details
    ISSN: 1432-072X
    Keywords: Escherichia coli ; Salmonella typhimurium ; murB ; rrfB ; Repetitive extragenic palindrome ; Evolution ; Mutation rate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The murB gene of Salmonella typhimurium was cloned and found to be 75% and 82% identical to the DNA and protein sequences, respectively, of the same gene in Escherichia coli. These identities are among the lowest recorded between the two bacteria. Nevertheless, wild-type S. typhimurium murB complemented the known temperature-sensitive E. coli mutant, and wild-type E. coli murB complemented three temperature-sensitive mutants of S. typhimurium. The 5S rRNA gene, rrfB, and the region between murB and rrfB were also cloned and sequenced. The rrfB gene of S. typhimurium differs from rrfB of E. coli in only 2 of 120 nt, but the region between murB and rrfB has diverged greatly and includes a sequence that elosely resembles a repetitive extragenic palindrome of the type normally associated with E. coli. Previous comparisons of gene divergence have suggested that the chromosomal mutation rate is lower in the vicinity of the origin of replication. However, the S. typhimurium murB gene, located 6 map minutes from the origin of replication, is highly substituted at synonymous sites and the sequence between murB and rrfB is significantly modified as well. Thus, murB is an exception to the general observation that genes near the origin of replication show less divergence than do genes elsewhere in the bacterial chromosome.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00307771
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  • 7
    Electronic Resource
    Electronic Resource
    The adaptive acid tolerance response in root nodule bacteria and Escherichia coli (1994)
    Springer
    Archives of microbiology 161 (1994), S. 286-292 
    Details
    ISSN: 1432-072X
    Keywords: Acid shock ; Rhizobium ; Bradyrhizobium ; Escherichia coli ; pH Tolerance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Root nodule bacteria and Escherichia coli show an adaptive acid tolerance response when grown under mildly acidic conditions. This is defined in terms of the rate of cell death upon exposure to acid shock at pH 3.0 and expressed in terms of a decimal reduction time, D. The D values varied with the strain and the pH of the culture medium. Early exponential phase cells of three strains of Rhizobium leguminosarum (WU95, 3001 and WSM710) had D values of 1, 6 and 5 min respectively when grown at pH 7.0; and D values of 5, 20 and 12 min respectively when grown at pH 5.0. Exponential phase cells of Rhizobium tropici UMR1899, Bradyrhizobium japonicum USDA110 and peanut Bradyrhizobium sp. NC92 were more tolerant with D values of 31, 35 and 42 min when grown at pH 7.0; and 56, 86 and 68 min when grown at pH 5.0. Cells of E. coli UB1301 in early exponential phase at pH 7.0 had a D value of 16 min, whereas at pH 5.0 it was 76 min. Stationary phase cells of R. leguminosarum and E. coli were more tolerant (D values usually 2 to 5-fold higher) than those in exponential phase. Cells of R. leguminosarum bv. trifolii 3001 or E. coli UB1301 transferred from cultures at pH. 7.0 to medium at pH 5.0 grew immediately and induced the acid tolerance response within one generation. This was prevented by the addition of chloramphenicol. Acidadapted cells of Rhizobium leguminosarum bv. trifolii WU95 and 3001; or E. coli UB1301, M3503 and M3504 were as sensitive to UV light as those grown at neutral pH.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00303582
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  • 8
    Electronic Resource
    Electronic Resource
    Occurrence of airborne enteric bacteria in Mexico city (1994)
    Springer
    Aerobiologia 10 (1994), S. 39-45 
    Details
    ISSN: 1573-3025
    Keywords: airborne bacteria ; urban environment ; Escherichia coli
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary An investigation of microbial air quality in the area of the National Autonomous University of Mexico, located in the southern part of Mexico City, was conducted for one year. Ambient outdoor concentrations and size distribution of airborne bacteria were measured, 130 samples were taken at noon, using an Andersen 6 stage sampler, located 2 m above ground level. Concentration ranges and colony-forming units per cubic meter of air (CFU m−3) found, were as follows:14 to 12999 for total bacteria, No growth (NG) to 55 for coliform bacteria, NG to 11 for fecal coliform and NG to 10 for fecal Streptococci. Bacteria associated with the potentially respirable fraction (0.65 to 4.7 µm) averaged 37% and 9% for total bacteria and coliform bacteria respectively. In 23% of the samples, coliform bacteria were recovered, with higher incidences during dry season. The most common of these were:Escherichia coli (15%), followed bySerratia (13%) andEnterobacter (10%), The total bacteria correlated significatively (p〈0.05) with the following parameters: particulate matter smaller than 10 µm (PM10) (r=0.40), total suspended particulates (TSP) (r=0.26), daily variation of temperature (r=0.18), and vapor pressure (r=−0.16). These relationships indicate that fecal soil pollution could affect air quality with potential health risks.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02066745
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  • 9
    Electronic Resource
    Electronic Resource
    Purification and characterization of pea thioredoxin f expressed in Escherichia coli (1994)
    Springer
    Plant molecular biology 26 (1994), S. 225-234 
    Details
    ISSN: 1573-5028
    Keywords: chloroplast ; Escherichia coli ; fructose 1,6-bisphosphatase ; light activation ; NADP-dependent malate dehydrogenase ; thioredoxin f
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The recently cloned cDNA for pea chloroplast thioredoxin f was used to produce, by PCR, a fragment coding for a protein lacking the transit peptide. This cDNA fragment was subcloned into a pET expression vector and used to transform E. coli cells. After induction with IPTG the transformed cells produce the protein, mainly in the soluble fraction of the broken cells. The recombinant thioredoxin f has been purified and used to raise antibodies and analysed for activity. The antibodies appear to be specific towards thioredoxin f and do not recognize other types of thioredoxin. The recombinant protein could activate two chloroplastic enzymes, namely NADP-dependent malate dehydrogenase (NADP-MDH) and fructose 1,6-bisphosphatase (FBPase), both using dithiothreitol as a chemical reductant and in a light-reconstituted/thylakoid assay. Recombinant pea thioredoxin f turned out to be an excellent catalyst for NADP-MDH activation, being the more efficient than a recombinant m-type thioredoxin of Chlamydomonas reinhardtii and the thioredoxin of E. coli. At the concentrations of thioredoxin used in the target enzyme activation assays only the recombinant thioredoxin f activated the FBPase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00039534
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  • 10
    Electronic Resource
    Electronic Resource
    Reconstitution of the spinach oxygen-evolving complex with recombinant Arabidopsis manganese-stabilizing protein (1994)
    Springer
    Plant molecular biology 26 (1994), S. 117-130 
    Details
    ISSN: 1573-5028
    Keywords: Escherichia coli ; inclusion bodies ; oxygen evolution ; pET vector ; photosystem II ; precursor protein ; processing psbo ; 33 kDa protein
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The psbO gene of cyanobacteria, green algae and higher plants encodes the precursor of the 33 kDa manganese-stabilizing protein (MSP), a water-soluble subunit of photosystem II (PSII). Using a pET-T7 cloning/expression system, we have expressed in Escherichia coli a full-length cDNA clone of psbO from Arabidopsis thaliana. Upon induction, high levels of the precursor protein accumulated in cells grown with vigorous aeration. In cells grown under weak aeration, the mature protein accumulated upon induction. In cells grown with moderate aeration, the ratio of precursor to mature MSP decreased as the optical density at induction increased. Both forms of the protein accumulated as inclusion bodies from which the mature protein could be released under mildly denaturing conditions that did not release the precursor. Renatured Arabidopsis MSP was 87% as effective as isolated spinach MSP in restoring O2 evolution activity to MSP-depleted PSII membranes from spinach; however, the heterologous protein binds to spinach PSIIs with about half the affinity of the native protein. We also report a correction to the previously published DNA sequence of Arabidopsis psbO (Ko et al., Plant Mol Biol 14 (1990) 217–227).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00039525
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  • 11
    Electronic Resource
    Electronic Resource
    RifR mutations in the beginning of the Escherichia coli rpoB gene (1994)
    Springer
    Molecular genetics and genomics 244 (1994), S. 120-126 
    Details
    ISSN: 1617-4623
    Keywords: Escherichia coli ; RNA polymerase ; Rifampicin ; RifR mutations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In Escherichia coli, mutations conferring rifampicin (Rif) resistance map to the rpoB gene, which encodes the 1342-amino acid β subunit of RNA polymerase. Almost all sequenced RifR mutations occur within the Rif region, encompassing rpoB codons 500–575. A strong RifR mutation lying outside the Rif region, which changed Val146 to Phe was previously reported, but was not recovered in subsequent studies. Here, we used site-directed mutagenesis followed by selection on Rif to search for RifR mutations in the evolutionarily conserved segment of rpoB around codon 146. Strong RifR mutations were obtained when Val146 was mutated, and several weak RifR mutations were also isolated near position 146. The results define a new, N-terminal cluster of RifR mutations, in addition to the classical central Rif region.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00283512
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  • 12
    Electronic Resource
    Electronic Resource
    Membrane topology and assembly of the outer membrane protein OmpA of Escherichia coli K12 (1994)
    Springer
    Molecular genetics and genomics 243 (1994), S. 127-135 
    Details
    ISSN: 1617-4623
    Keywords: Escherichia coli ; Outer membrane OmpA protein ; Membrane topology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The 325-residue outer membrane protein OmpA of Escherichia coli has been proposed to consist of a membrane-embedded moiety (residues 1 to about 170) and a C-terminal periplasmic region. The former is thought to comprise eight transmembrane segments in the form of antiparallel β-strands, forming an amphiphilic β connected by exposed turns. Several questions concerning this model were addressed. Thus no experimental evidence had been presented for the turns at the inner leaflet of the membrane and it was not known whether or not the periplasmic part of the polypeptide plays a role in the process of membrane incorporation. Oligonucleotides encoding trypsin cleavage sites were inserted at the predicted turn sites of the ompA gene and it was shown that the encoded proteins indeed become accessible to trypsin at the modified sites. Together with previous results, these data also show that the turns on both sides of the membrane do not possess specifically topogenic information. In two cases one of the two expected tryptic fragments was lost and could be detected at low concentration in only one case. Therefore, bilateral proteolytic digestion of outer membranes can cause loss of β-strands and does not necessarily produce a reliable picture of protein topology. When ompA genes were constructed coding for proteins ending at residue 228 or 274, the membrane assembly of these proteins was shown to be partially defective with about 20% of the proteins not being assembled. No such defect was observed when, following the introduction of a premature stop codon, a truncated protein was produced ending with residue 171. It is concluded that (1) the proposed β-barrel structure is essentially correct and (2) the periplasmic part of OmpA does not play an active role in, but can, when present in mutant form, interfere with membrane assembly.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00280309
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  • 13
    Electronic Resource
    Electronic Resource
    New killing system controlled by two genes located immediately upstream of the mukB gene in Escherichia coli (1994)
    Springer
    Molecular genetics and genomics 243 (1994), S. 136-147 
    Details
    ISSN: 1617-4623
    Keywords: Escherichia coli ; Plasmid Post-segregational killing system ; kicA ; kicB
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The nucleotide sequence was determined of the region upstream of the mukB gene of Escherichia coli. Two new genes were found, designated kicA and kicB (killing of cell); the gene order is kicB-kicA-mukB. Promoter activities were detected in the regions immediately upstream of kicB and kicA, but not in front of mukB. Gene disruption experiments revealed that the kicA disruptant was nonviable, but the kicB-disrupted mutant and the mutant lacking both the kicB and kicA genes were able to grow. When kicA disruptant cells bearing a temperature-sensitive replication plasmid carrying the kicA + gene were grown at 30° C and then transferred to 42° C, the mutant cells gradually lost colony-forming ability, even in the presence of a mukB + plasmid. Rates of protein synthesis, but not of RNA or DNA synthesis, fell dramatically during incubation at 42° C. These results suggested that the kicB gene encodes a killing factor and the kicA gene codes for a protein that suppresses the killing function of the kicB gene product. It was also demonstrated that KicA and KicB can function as a post-segregational killing system, when the genes are transferred from the E. coli chromosome onto a plasmid.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00280310
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  • 14
    Electronic Resource
    Electronic Resource
    Predicted fitness changes along an environmental gradient (1994)
    Springer
    Evolutionary ecology 8 (1994), S. 524-541 
    Details
    ISSN: 1573-8477
    Keywords: Escherichia coli ; environmental gradient ; fitness ; lactose operon
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The relations between enzyme activity and the intensity of selection across an environmental gradient are investigated usingEscherichia coli growing on mixed resources. Experimental results demonstrate that the direction and intensity of natural selection can be predicted solely from a knowledge of the underlying biochemistry, physiology and ecology of the organism. Ecological theory, based on the logistic equation, is unable to use this information to predict the outcome of competition — the best it can do is to fit constants to data points. Our results also suggest that partitioning of the phenotypic variance using quantitative genetics need not correspond to the underlying molecular structure generating phenotypes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01238256
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  • 15
    Electronic Resource
    Electronic Resource
    Escherichia coli mutY-dependent mismatch repair involves DNA polymerase I and a short repair tract (1994)
    Springer
    Molecular genetics and genomics 244 (1994), S. 444-450 
    Details
    ISSN: 1617-4623
    Keywords: Escherichia coli ; mutY ; DNA mismatch repair ; DNA polymerase ; Repair tract
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Repair of heteroduplex DNA containing an A/G mismatch in a mutL background requires the Escherichia coli mutY gene function. The mutY-dependent in vitro repair of A/G mismatches is accompanied by repair DNA synthesis on the DNA strand bearing mispaired adenines. The size of the mufY-dependent repair tract was measured by the specific incorporation of α-[32P]dCTP into different restriction fragments of the repaired DNA. The repair tract is shorter than 12 nucleotides and longer than 5 nucleotides and is localized to the 3′ side of the mismatched adenine. This repair synthesis is carried out by DNA polymerase I.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00286698
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  • 16
    Electronic Resource
    Electronic Resource
    A pleîotropic acid phosphatase-deficient mutant of Escherichia coli shows premature termination in the dsbA gene. Use of dsbA :: phoA furions to localize a structurally important domain in DsbA (1994)
    Springer
    Molecular genetics and genomics 242 (1994), S. 23-32 
    Details
    ISSN: 1617-4623
    Keywords: Escherichia coli ; Acid phosphatase ; DsbA factor ; Periplasmic space ; Proteolysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A one-step mutant of Escherichia coli K-12 lacking both glucose-1-phosphatase (Agp) and pH 2.5 acid phosphatase (AppA) activities in the periplasmic space was isolated. The mutation which mapped close to ch1B, at 87 min on the E. coli linkage map, also caused the loss of alkaline phosphatase (PhoA) activity, even when this activity was expressed from TnphoA fusions to genes encoding periplasmic or membrane proteins. A DNA fragment that complements the mutation was cloned and shown to carry the dsbA gene, which encodes a periplasmic disulphide bond-forming factor. The mutant had an ochre triplet in dsbA, truncating the protein at amino acid 70. Introduction of TnphoA fusions into a plasmid-borne dsbA gene resulted in DsbA-PhoA hybrid proteins that were all exported to the periplasmic space in both dsbA + and dsbA strains. They belong to three different classes, depending on the length of the DsbA fragment fused to PhoA. When PhoA was fused to an amino-terminal DsbA heptapeptide, the protein was only seen in the periplasm of a dsbA + strain, as in the case of wild-type PhoA. Hybrid proteins missing up to 29 amino acids at the carboxy-terminus of DsbA were stable and retained both the DsbA and PhoA activities. Those with shorter DsbA fragments that still carried the -Cys-ProHis-Cys-motif were rapidly degraded (no DsbA activity). The presence is discussed of a structural domain lying around amino acid 170 of DsbA and which is probably essential for its folding into a proteolytic-resistant and enzymatically active form.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00277344
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  • 17
    Electronic Resource
    Electronic Resource
    Identification and preliminary characterization of temperature-sensitive mutations affecting HlyB, the translocator required for the secretion of haemolysin (HlyA) from Escherichia coli (1994)
    Springer
    Molecular genetics and genomics 245 (1994), S. 431-440 
    Details
    ISSN: 1617-4623
    Keywords: Haemolysin ; Secretion ; Escherichia coli ; K-12 ; HlyB
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We have carried out a genetic analysis of Escherichia coli HlyB using in vitro(hydroxylamine) mutagenesis and regionally directed mutagenesis. From random mutagenesis, three mutants, temperature sensitive (Ts) for secretion, were isolated and the DNA sequenced: Glyl0Arg close to the N-terminus, Gly408Asp in a highly conserved small periplasmic loop region PIV, and Pro624Leu in another highly conserved region, within the ATP-binding region. Despite the Ts character of the Gly10 substitution, a derivative of HlyB, in which the first 25 amino acids were replaced by 21 amino acids of the λ Cro protein, was still active in secretion of HlyA. This indicates that this region of HlyB is dispensable for function. Interestingly, the Gly408Asp substitution was toxic at high temperature and this is the first reported example of a conditional lethal mutation in HlyB. We have isolated 4 additional mutations in PIV by directed mutagenesis, giving a total of 5 out of 12 residues substituted in this region, with 4 mutations rendering HlyB defective in secretion. The Pro624 mutation, close to the Walker B-site for ATP binding in the cytoplasmic domain is identical to a mutation in HisP that leads to uncoupling of ATP hydrolysis from the transport of histidine. The expression of a fully functional haemolysin translocation system comprising HlyC,A,B and D increases the sensitivity of E. coli to vancomycin 2.5-fold, compared with cells expressing HlyB and HlyD alone. Thus, active translocation of HlyA renders the cells hyperpermeable to the drug. Mutations in hlyB affecting secretion could be assigned to two classes: those that restore the level of vancomycin resistance to that of E. coli not secreting HlyA and those that still confer hypersensitivity to the drug in the presence of HlyA. We propose that mutations that promote vancomycin resistance will include mutations affecting initial recognition of the secretion signal and therefore activation of a functional transport channel. Mutations that do not alter HlyA-dependent vancomycin sensitivity may, in contrast, affect later steps in the transport process.
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    URL: http://dx.doi.org/10.1007/BF00302255
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    Location of the ompT gene relative to that of appY on the physical map of the Escherichia coli chromosome (1994)
    Springer
    Molecular genetics and genomics 242 (1994), S. 363-364 
    Details
    ISSN: 1617-4623
    Keywords: Escherichia coli ; Physical map ; ompT ; appY ; Gene order
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Results concerning the precise location of the ompT gene (encoding the outer membrane protease OmpT) on the Escherichia coli chromosome were obtained which disagree with published restriction sites in the gene. It is shown that the gene, together with appY, is present on a 3.075 PstI fragment, encompassing positions 596–598 of the E. coli physical map.
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    URL: http://dx.doi.org/10.1007/BF00280427
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    Structure of the 5′ upstream region and the regulation of the rpoS gene of Escherichia coli (1994)
    Springer
    Molecular genetics and genomics 243 (1994), S. 525-531 
    Details
    ISSN: 1617-4623
    Keywords: Escherichia coli ; RNA polymerase sigma factor ; rpoS ; Stationary phase ; Post-translational regulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The nucleotide sequence of the 5′ upstream region of the Escherichia coli rpoS gene was determined and analyzed. At least four promoters responsible for rpoS transcription were identified, and designated P1, P2, P3 andP4, P1 being furthest from the upstream. Using lacZ fusion genes, the P2 promoter was found to be the strongest of the four. All of these promoters are regulated similarly, and their activity is enhanced 2 to 3-fold in stationary phase. P1 and P2 transcription start sites were determined by primer extension analyses. The P2 promoter region shows similarity to the consensus σ70-type promoter sequence, and was recognized by both Eσ70 and Eσ38 holoenzymes in vitro. The mRNA transcribed from the most distal promoter, P1, appears to include another open reading frame (orf-281), indicating that the two open reading frames comprise an operon. The rpoS gene product (σ38) was rapidly degraded after addition of chloramphenicol to cultures in the exponential, but not the stationary phase. This strongly suggests that posttranslational regulation is involved in the control of rpoS expression.
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    Transposable elements and adaptation of host bacteria (1994)
    Springer
    Genetica 93 (1994), S. 5-12 
    Details
    ISSN: 1573-6857
    Keywords: Escherichia coli ; transposable elements ; adaptation ; evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A transposable element (TE) is a mobile sequence present in the genome of an organism. TEs can cause lethal mutations by inserting into essential, genes, promoting deletions or leaving short sequences upon excision. They therefore may be gradually eliminated from mixed populations of haploid micro-organisms such asEscherichia coli if they cannot balance this mutation load. Horizontal transmission between cells is known to occur and promote the transfer of TEs, but at rates often too low to compensate for the burden to their hosts. Therefore, alternative mechanisms should be found by these elements to earn their keep in the cells. Several theories have been suggested to explain their long-term maintenance in prokaryotic genomes, but little molecular evidence has been experimentally obtained. In this paper, the permanence of transposable elements in bacterial populations is discussed in terms of costs or benefits for the element and for the host. It is observed that, in all studies yet reported, the elements do not behave in their host as selfish DNA but as a co-operative component for the evolution of the couple.
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    URL: http://dx.doi.org/10.1007/BF01435235
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    A temperature-sensitive mutant ofEscherichia coli with an alteration in ribosomal protein L22 (1994)
    Springer
    Genetica 94 (1994), S. 17-25 
    Details
    ISSN: 1573-6857
    Keywords: ribosomal protein ; ts mutant ; protein L22 ; Escherichia coli
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A temperature-sensitive, protein synthesis-defective mutant ofEscherichia coli exhibiting an altered ribosomal protein L22 has been investigated. The temperature-sensitive mutation was mapped to therplV gene for protein L22. The genes from the wild type and mutant strains were amplified by the polymerase chain reaction and the products were sequenced. A cytosine to thymine transition at position 22 of the coding sequence was found in the mutant DNA, predicting an arginine to cysteine alteration in the protein. A single cysteine residue was found in the isolated mutant protein. This amino acid change accounts for the altered mobility of the mutant protein in two-dimensional gels and during reversed-phase HPLC. The temperature-sensitive phenotype was fully complemented by a plasmid carrying the wild type L22 gene. Ribosomes from the complemented cells showed only wild type protein L22 by two dimensional gel analysis and were as heat-resistant as control ribosomes in a translation assay. The point mutation in the L22 gene is uniquely responsible for the temperature-sensitivity of this strain.
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    URL: http://dx.doi.org/10.1007/BF01429216
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    The hydrogenases and formate dehydrogenases ofEscherichia coli (1994)
    Springer
    Antonie van Leeuwenhoek 66 (1994), S. 57-88 
    Details
    ISSN: 1572-9699
    Keywords: Formate dehydrogenases ; hydrogenases ; Escherichia coli ; anaerobic metabolism ; regulation of gene expression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Escherichia coli has the capacity to synthesise three distinct formate dehydrogenase isoenzymes and three hydrogenase isoenzymes. All six are multisubunit, membrane-associated proteins that are functional in the anaerobic metabolism of the organism. One of the formate dehydrogenase isoenzymes is also synthesised in aerobic cells. Two of the formate dehydrogenase enzymes and two hydrogenases have a respiratory function while the formate dehydrogenase and hydrogenase associated with the formate hydrogenlyase pathway are not involved in energy conservation. The three formate dehydrogenases are molybdo-selenoproteins while the three hydrogenases are nickel enzymes; all six enzymes have an abundance of iron-sulfur clusters. These metal requirements alone invoke the necessity for a profusion of ancillary enzymes which are involved in the preparation and incorporation of these cofactors. The characterisation of a large number of pleiotropic mutants unable to synthesise either functionally active formate dehydrogenases or hydrogenases has led to the identification of a number of these enzymes. However, it is apparent that there are many more accessory proteins involved in the biosynthesis of these isoenzymes than originally anticipated. The biochemical function of the vast majority of these enzymes is not understood. Nevertheless, through the construction and study of defined mutants, together with sequence comparisons with homologous proteins from other organisms, it has been possible at least to categorise them with regard to a general requirement for the biosynthesis of all three isoenzymes or whether they have a specific function in the assembly of a particular enzyme. The identification of the structural genes encoding the formate dehydrogenase and hydrogenase isoenzymes has enabled a detailed dissection of how their expression is coordinated to the metabolic requirement for their products. Slowly, a picture is emerging of the extremely complex and involved path of events leading to the regulated synthesis, processing and assembly of catalytically active formate dehydrogenase and hydrogenase isoenzymes. This article aims to review the current state of knowledge regarding the biochemistry, genetics, molecular biology and physiology of these enzymes.
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    Crotonobetaine reductase fromEscherichia coli — a new inducible enzyme of anaerobic metabolization of L(-)-carnitine (1994)
    Springer
    Antonie van Leeuwenhoek 65 (1994), S. 63-69 
    Details
    ISSN: 1572-9699
    Keywords: L(-)-carnitine ; crotonobetaine ; crotonobetaine reductase ; Escherichia coli
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Crotonobetaine reductase fromEscherichia coli 044 K74 is an inducible enzyme detectable only in cells grown anaerobically in the presence of L(-)-carnitine or crotonobetaine as inducers. Enzyme activity was not detected in cells cultivated in the presence of inducer plus glucose, nitrate, γ-butyrobetaine or oxygen, respectively. Fumarate caused an additional stimulation of growth and an increased expression of crotonobetaine reductase. The reaction product, γ-butyrobetaine, was identified by autoradiography. Crotonobetaine reductase is localized in the cytoplasm, and has been characterized with respect to pH (pH 7.8) and temperature optimum (40–45 °C). The K m value for crotonobetaine was determined to be 1.1×10−2M. γ-Butyrobetaine,D(+)-carnitine and choline are inhibitors of crotonobetaine reduction. For γ-butyrobetaine (K i =3×10−5M) a competitive inhibition type was determined. Various properties suggest that crotonobetaine reductase is different from other reductases of anaerobic respiration.
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    Nitrate reductases inEscherichia coli (1994)
    Springer
    Antonie van Leeuwenhoek 66 (1994), S. 47-56 
    Details
    ISSN: 1572-9699
    Keywords: Anaerobiosis ; Escherichia coli ; Fnr ; narL ; nitrate ; nitrate reductase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Escherichia coli expresses two different membrane-bound respiratory nitrate reductases, nitrate reductase A (NRA) and nitrate reductase Z (NRZ). In this review, we compare the genetic control, biochemical properties and regulation of these two closely related enzyme systems. The two enzymes are encoded by distinct operons located within two different loci on theE. coli chromosome. ThenarGHJI operon, encoding nitrate reductaseA, is located in thechlC locus at 27 minutes, along with several functionally related genes:narK, encoding a nitrate/nitrite antiporter, and thenarXL operon, encoding a nitrate-activated, two component regulatory system. ThenarZYWV operon, encoding nitrate reductase Z, is located in thechlZ locus located at 32.5 minutes, a region which includes anarK homologue,narU, but no apparent homologue to thenarXL operon. The two membrane-bound enzymes have similar structures and biochemical properties and are capable of reducing nitrate using normal physiological substrates. The homology of the amino acid sequences of the peptides encoded by the two operons is extremely high but the intergenic regions share no related sequences. The expression of both thenarGHJI operon and thenarK gene are positively regulated by two transacting factors Fnr and NarL-Phosphate, activated respectively by anaerobiosis and nitrate, while thenarZYWV operon and thenarU gene are constitutively expressed. Nitrate reductase A, which accounts for 98% of the nitrate reductase activity when fully induced, is clearly the major respiratory nitrate reductase inE. coli while the physiological role of the constitutively expressed nitrate reductase Z remains to be defined.
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    A simple procedure to obtain plasmids suitable for transfecting mammalian cell lines (1994)
    Springer
    World journal of microbiology and biotechnology 10 (1994), S. 346-347 
    Details
    ISSN: 1573-0972
    Keywords: Chromatography ; Escherichia coli ; plasmid ; transfection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract A simple procedure to obtain plasmid preparations, suitable for transfecting mammalian cell lines using a calcium phosphate co-precipitation technique, is described. The protocol is based on the purification of plasmid DNA by double gel-filtration chromatography on Sephacryl S-1000 and additional slight modifications to the original transfection procedure. The purity of plasmid preparation was verified by analytical methods. The resulting preparation efficiently transfected NIH-3T3 cells.
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    Structured model of genetic control via the lac promoter in Escherichia coli (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 43 (1994), S. 399-410 
    Details
    ISSN: 0006-3592
    Keywords: lac-based promoters ; Escherichia coli ; genetic control ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A model that describes induction of protein synthesis from lac-based promoters has been developed and incorporated into the single-cell model of Escherichia coli with transcriptional and translational modifications. Unlike previous models of lac-based promoters, this model allows a priori prediction of the intracellular parameters controlling transcription from lac-based promoters with only the extracellular levels of substrate and inducer as inputs. Because of the structural detail of the model, it is possible to simulate different genetic constructions for comparison, such as Laclq strains versus wild-type cells, or including lacl on a multicopy plasmid. Expression from lac to tac promoters is predicted to yield 5% and 30% of the total cellular protein, respectively, with a pBR322-type plasmid. The model predicts the experimental observation that the Laclq strain is not as fully induced as the wild-type strains, even at higher inducer concentrations. Additionally, the model predicts the right order of magnitude of protein production from lac and tac promoters when mechanisms for attenuation of transcription at lower translational efficiency are considered. Finally, the model predicts that for high copy number systems ribosomes become limiting in the synthesis of plasmid-encoded proteins. © 1994 John Wiley & Sons, Inc.
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    Overproduction of glycogen in Escherichia coli blocked in the acetate pathway improves cell growth (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 44 (1994), S. 132-139 
    Details
    ISSN: 0006-3592
    Keywords: glycogen ; Escherichia coli ; cell growth ; acetate ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Excessive production of acetate is a problem frequently encountered in aerobic high-cell-density fermentations of Escherichia coli. Here, we have examined genetic alterations resulting in glycogen overproduction as a possible means to direct the flux of carbon away from the acetate pool. Glycogen overaccumulation was achieved either by using a regulatory glgQ mutation or by transforming cells with a plasmid containing the glycogen biosynthesis genes glgC (encoding ADPG pyrophosphorylase) and glgA (encoding glycogen synthase) under their native promoter. Both strategies resulted in an approximately five-fold increase in glycogen levels but had no significant effect on acetate excretion. The glgC and glgA genes were then placed under the control of the isopropyl---D-thiogalactopyranoside (IPTG) inducible tac promoter, and this construct was used to stimulate glycogen production in a mutant defective in acetate biosynthesis due to deletion of the ack (acetate kinase) and pta (phosphotransacetylase) genes. If glycogen overproduction in the ack pta strain was induced during the late log phase, biomass production increased by 15 to 20% relative to uninduced controls. Glycogen overaccumulation had a significant influence on carbon partitioning: The output of carbon dioxide peaked earlier than in the control strain, and the levels of an unusual fermentation byproduct, pyruvate, were reduced. Exogenous pyruvate was metabolized more rapidly, suggesting higher activity of gluconeogenesis or the tricarboxylic acid (TCA) cycle as a result of glycogen overproduction. Potential mechanisms of the observed metabolic alterations are discussed. Our results suggest that ack pta mutants over producing glycogen may be a suitable starting point for constructing E. coli strains with improved characteristics in high-cell-density fermentations. © 1994 John Wiley & Sons, Inc.
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    Predictions for oxygen supply control to enhance population stability of engineered production strains (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 43 (1994), S. 275-285 
    Details
    ISSN: 0006-3592
    Keywords: Escherichia coli ; amino acids ; linear optimization ; metabolic fluxes ; metabolic engineering ; culture stability ; oxygen ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The simultaneous growth and product formation in a microbial culture is an important feature of several laboratory, industrial, and environmental bioprocesses. Metabolic burden associated with product formation in these bioprocesses may lead to growth advantage of a nonproducing mutant leading to a loss of the producing population over time. A simple population dynamics model demonstrates the extreme sensitivity of population stability to the engineered productivity of a strain. Here we use flux balance analysis to estimate the effects of the metabolic burden associated with product secretion on optimal growth rates. Comparing the optimal growth rates of the producing and nonproducing strains under a given processing condition allows us to predict the population stability. In order to increase stability of an engineered strain, we determine processing conditions that simultaneously maximize the growth rate of the producing population while minimizing the growth rate of a nonproducing population. Using valine, tryptophan, and lysine production as specific examples, we demonstrate that although an appropriate choice of oxygenation may increase culture longevity more than twofold, total production as governed by economic criterion can be increased by several orders of magnitude. Choice of optimal nutrient and oxygen supply rates to enhance stability is important both for strain screening as well as for culture of engineered strains. Appropriate design of the culture environment can thus be used to enhance the productivity of bioprocesses that use engineered production strains. © 1994 John Wiley & Sons, Inc.
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    Ribosomal protein limitations in Escherichia coli under conditions of high translational activity (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 43 (1994), S. 388-398 
    Details
    ISSN: 0006-3592
    Keywords: ribosome synthesis ; Escherichia coli ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Details of the mechanism for ribosome synthesis have been incorporated in the single-cell Escherichia coli model, which enable us to predict the amount of protein synthesizing machinery under different environmental conditions. The predictions agree quite well with available experimental data. The model predicts that ribosomal protein limitations are important when the translational apparatus is in high demand. Ribosomal RNA synthesis is induced by an increase in translational activity, which, in turn, stimulates ribosomal protein synthesis. However, as the demand increases still more, the ribosomal protein mRNA must compete with the plasmid mRNA for ribosomes, and the efficiency of translation of ribosomal proteins is reduced. © 1994 John Wiley & Sons, Inc.
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    Physicochemical properties of the matrix proteins of three main culture vehicles (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 44 (1994), S. 29-37 
    Details
    ISSN: 0006-3592
    Keywords: proteins, contaminant ; Escherichia coli ; Saccharomyces cerevisiae ; mammalian cell culture ; PAGE ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The protein components of three industrial recombinant expression systems: Escherichia coli, Saccharomyces cerevisiae, and a mammalian cell culture supernatant of CHO cells were characterized in terms of their molecular weight, isoelectric point, and relative surface hydrophobicity. Identification of individual proteins was done by reference to their position in protein band profiles by polyacrylamide gel electrophoresis (PAGE) of the crude material. This permitted a rapid and facile assignment of quantitative values for these three parameters to all the major protein components in these materials. Because it is the indigenous proteins in expression systems that will form the bulk of any impurities in the product, once the values of these parameters are known for any target recombinant protein, the data obtained will enable appropriate expression systems to be chosen for minimizing amounts of potential contaminants and reducing downstream processing requirements and costs. The data will also indicate which fractionation steps (i.e., charge, size or hydrophobicity-based) are likely to be best for distinguishing between target and contaminant proteins, thus aiding and early removal of the maximum quantities of undesired protein to bring subsequent bioseparation steps down in scale and cost and up in terms of efficiency. © 1994 John Wiley & Sons, Inc.
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    Influence of strain and medium composition on filtration of escherichia coli suspensions (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 44 (1994), S. 539-548 
    Details
    ISSN: 0006-3592
    Keywords: cross-flow filtration ; Escherichia coli ; cell harvesting ; fermentation ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Cross-flow filtration of Escherichia coli strains was examined at the laboratory and pilot scales using Romicon 500,000 molecular-weight-cutoff hollow fiber membranes. Both the series resistance and macrosolute polarization models were employed to compare performances. Total dissolved solids content above 90 g/L and viscosity above 1.1 × 10-3 paċ s of cell-free culture media were found to decrease average filtration fluxes by over 60% both in the absence and presence of cells. Broth filtration with culture media of dissolved solids levels below 80 g/L were influenced to a greater extent by harvest cell density. The collodial nature of the complex nutrient responsible for the total solids increase affected prediction of filtration performance. Differences in strain filterability were observed with JM109 preferred over DH5 in high solids-containing media and RR1 preferred over JM109 in low dissolved solids-containing media. Their research demonstrates the importance of cell strain and media selection in the performance of early downstream processing steps. © 1994 John Wiley & Sons, Inc.
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    Purification and processing of cellulose-binding domain-alkaline phosphatase fusion proteins (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 44 (1994), S. 1295-1305 
    Details
    ISSN: 0006-3592
    Keywords: Escherichia coli ; fusion proteins ; Cellulomonas fimi ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Fusion of the leader peptide and the cellulose-binding domain (CBD) of endoglucanase A (CenA) from Cellulomonas fimi, with of without linker sequences, to the N-terminus of alkaline phosphatase (PhoA) from Escherichia coli leads to the accumulation of significant amounts of the CBD-PhoA fusion proteins in the supernatants of E. coli cultures. The fusion proteins can be purified from the supernatants by affinity chromatography on cellulose. The fusion protein can be desorbed from the cellulose with water or guanidine-HCl. If the sequence IEGR in present between the CBD and PhoA, the CBD can be cleaved from the PhoA with factor Xa. The efficiency of hydrolysis by factor Xa is strongly in fluenced by the amino acids on either side of the IEGR sequence. The CBD released by factor Xa is removed by adsorption to cellulose. A nonspecific proteases from C. fimi, which hydrolyzes native CenA between the CBD and the catalytic domain, may be useful for removing the CBD from some fusion proteins. © 1994 John Wiley & Sons, Inc.
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    Comparison of recombinant Escherichia coli strains for synthesis and accumulation of poly-(3-hydroxybutyric acid) and morphological changes (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 44 (1994), S. 1337-1347 
    Details
    ISSN: 0006-3592
    Keywords: poly-(3-hydroxybutyric acid) ; PHB ; Escherichia coli ; morphology ; plasmid ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A stable high-copy-number plasmid pSYL105 containing the Alcaligenes eutrophus polyhydroxyalkanoic acid (PHA) biosynthesis genes was constructed. This plasmid was transferred to seven Escherichia coli strains (K12, B, W, XL1-Blue, JM109, DH5α, and HB101), which were subsequently compared for their ability to synthesize and accumulate ploy- (3-hydroxybutyric acid) (PHB). Growth of recombinant cells and PHB synthesis were investigated in detail in Luria-Bertani (LB) medium containing 20 g/L glucose. Cell growth, the rate of PHB synthesis, the extent of PHB accumulation, the amount of glucose utilized, and the amount of acetate formed varied from one strain to another. XL1-Blue (pSYL105) and B (pSYL105) synthesized PHB at the fastest rate, which was ca. 0.2 g PHB/g true cell mass-h, and produced PHB up to 6-7 g/L. The yields of cell mass, true cell mass, and PHB varied considerably among the strains. The PHB yield of XL1-Blue (pSYL105) in LB plus 20 g/L glucose was as high as 0.369 g PHB/g glucose. Strains W (pSYL105) and K12 (pSYL105) accumulated the least amount of PHB with the lowest PHB yield at the lowest synthesis rate. JM109 (pSYL105) accumulated PHB to the highest extent (85.6%) with relatively low true cell mass (0.77 g/L). Considerable filamentation of cells accumulating PHB was observed for all strains except for K12 and W, which seemed to be due either to the overexpression of the foreign PHA biosynthesis enzymes or to the accumulation of PHB. © 1994 John Wiley & Sons, Inc.
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    Electrochemical disinfection of bacteria in drinking water using activated carbon fibers (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 43 (1994), S. 429-433 
    Details
    ISSN: 0006-3592
    Keywords: disinfection ; Escherichia coli ; water disinfection ; activated carbon fiber ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A novel electrochemical reactor employing activated carbon fiber (ACF) electrodes was constructed for disinfecting bacteria in drinking water. Escherichia coli adsorbed preferentially onto ACF rather than to carbon-cloth or granular-activated carbon. E. coli cells, which adsorbed onto the ACF, were killed electrochemically when a potential of 0.8 V vs. a saturated calomel electrode (SCE) was applied. Drinking water was passed through the reactor in stop-flow mode: 2mL/min for 12 h, o L/min for 24 h, and 1 mL/min for 6 h. At an applied potential of 0.8 V vs, SCE, viable cell concentration reamined below 30 cells/mL. In the absence of an applied potential, bacteria grew to a maximum concentration of 9.5 × 103 cells/mL. After continuous operation at 0.8 V vs. SCE, cells adsorbed onto the ACF could not be observed by scanning electron microscopy. In addition, chlorine in drinking water was completely removed by the reactor. Therefore, clean and efficient inactivation of bacteria in drinking water was successfully performed. © 1994 John Wiley & Sons, Inc.
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    URL: http://dx.doi.org/10.1002/bit.260430511
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    Effects of medium carbon-to-nitrogen ratio on biofilm formation and plasmid stability (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 44 (1994), S. 329-336 
    Details
    ISSN: 0006-3592
    Keywords: biofilm formation ; Escherichia coli ; C/N ratio ; plasmid retention ; extracellular polysaccharide ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Biofilm formation and plasmid segregational instability in biofilm cultures of Escherichia coli DH5α (pMJR1750) were investigated under different medium-carbon-to-nitrogen (C/N) ratios. At C/N ratios of 0.07 and 1, net accumulation of both biofilm plasmid-bearing and plasmid-free cells continued through the entire experiment without attaining any apparent steady state. At C/N ratios of 5 and 10, net biofilm cell accumulation for the two populations reached apparent steady states after 84 and 72 h, respectively. At C/N ratios of 0.07 and 1, polysaccharide production increased slowly and reached about 2g alginate equivalent/cm2 by the end of both experiments. At a C/N ratio of 5, polysaccharide increase significantly after 84 h, reaching about 7μg alginate equivalent/cm2 prior to termination. At a C/N ratio of 10, polysaccharide increased significantly after 72 h and reached 21 μg alginate equivalent/cm2 at 108 h. At C/N ratios of 0.07 and 1, protein production reached 6.5 and 4 μg/cm2, respectively. At C/N ratios of 5 and 10, protein production increased slightly for the first 84 h and reached a maximum at 108 h, at 3 and 2 μg/cm2, respectively, then decreased over the last 12 h of the experiment. Ratios of polysaccharide to protein increased with increasing C/N ratios. At C/N ratios of 0.07 and 1, the ratios between extracellular polysaccharide (EP) and protein were no more than 205 μg polysaccharide/μg protein, whereas those at C/N ratios of 5 and 10 increased to about 7 and 12 μg polysaccharide/μg protein, respectively.Probabilities of plasmid loss in the biofilm cultures increased with increasing C/N ratios. At C/N ratios of 0.07, 1, and 5, the probabilities of plasmid loss were 0.0013 ± 0.011, 0.020 ± 0.006 and 0.122 ± 0.021, respectively. At a C/N ratio of 10, the probability of plasmid loss was significantly higher, reaching 0.38 ± 0.125. The increase of probability of plasmid loss at higher C/N ratios results from competition between cell replication and extracellular polysaccharide production. © 1994 John Wiley & Sons, Inc.
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    A metabolic model of cellular energetics and carbon flux during aerobic Escherichia coli fermentation (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 43 (1994), S. 847-855 
    Details
    ISSN: 0006-3592
    Keywords: Escherichia coli ; cellular energetics ; acetate production ; carbon yield ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An integrated metabolic model for the production of acetate by Escherichia coli growing on glucose under aerobic conditions was presented previously (Ko et al., 1993). The resulting model equations can be used to explain phenomena often observed with industrial fermentations, i.e., increased acetate production which follows from high glucose uptake rate, a low dissolved oxygen concentration, a high specific growth rate, or a combination of these conditions. However, several questions still need to be addressed. First, cell composition is growth rate and media dependent. Second, the macromolecular composition varied between E. coli strains. And finally, a model that represents the carbon fluxes between the Embden-Meyerhof-Parnas (EMP) and the hexose monophosphate (HMP) pathways when cells are subject to internal and/or external stresses is still not well defined. In the present work, we have made an effort to account for these effects, and the resulting model equations show good agreement for wild-type and recombinant E. coli experimental data for the acetate concentration, the onset of acetate secretion, and cell yield based on glucose. These results are useful for optimizing aerobic E. coli fermentation processes. More specifically, we have determined the EMP pathway carbon flux profiles required by the integrated metabolic model for an accurate fit of the acetic acid profile data from a wild-type E. coli strain ML308. These EMP carbon flux profiles were correlated with a dimensionless measurement of biomass and then used to predict the acetic acid profiles for E. coli strain F-122 expressing human immunodeficiency virus-(HIV528) β-galactosidase fusion protein. The effect of different macromolecular compositions and growth rates between these two E. coli strains required a constant scaling factor for improved quantitative predictions.
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    Modification of central metabolic pathway in escherichia coli to reduce acetate accumulation by heterologous expression of the bacillus subtilis acetolactate synthase gene (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 44 (1994), S. 944-951 
    Details
    ISSN: 0006-3592
    Keywords: acetate reduction ; Bacillus subtilis ; Escherichia coli ; cloning ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A novel metabolic engineering technique involving the redirection ofcellular carbon fluxes was employed to reduce acetate production in an Escherichia coli culture. Metabolic engineering was achieved by cloning E. coli the gene for the Bacillus subtilis acetolactate synthase (ALS), an enzyme capable of catalyzing the conversion of pyruvate to nonacidic and less harmful species. The heterologous expression of the ALS catabolic enzyme in Escherichia coli drastically modified the cellular glycolytic fluxes. In particular, acetate excretion, which is a common characteristic of E. coli, as well as a physiological burden, was minimized. The residual acetate level was kept under control and maintained at a level that was below the toxic threshold. The expression of the biologically active ALS enzyme in E. coli did not result in any detectable changes on either cell growth rate or cell yields. The alternative product, acetoin, was shown to be 50 times less harmful than acetate. Similarities in the growth pattern of two different E. coli strains, RR1 and GJT001, under all cultivation conditions suggested that the ability of ALS to reduce acetate accumulation is generic and not strain-specific. © 1994 John Wiley & Sons, Inc.
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    Effect of modified glucose uptake using genetic engineering techniques on high-level recombinant protein production in escherichia coli dense cultures (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 44 (1994), S. 952-960 
    Details
    ISSN: 0006-3592
    Keywords: Escherichia coli ; protein production, recombinant ; glucose uptake ; acetate excretion ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Reduction of acetate excretion using a modified cellular glucose uptake rate was examined. An Escherichia coli strain bearing a mutationin ptsG, a gene encoding enzyme II in glucose phosphotransferase system (PTS), was constructed and characterized. The growth rate of the mutant strain was slower than its parent in glucose defined medium, butwas not affected in complex medium. Experimental results using this mutant strain showed a significant improvement in culture performance in simple batch cultivations due to reduced acetate excretion through the modified glucose uptake. Both biomass and recombinant protein productivity were increased by more than 50% with the ptsG mutant when compared to the parent strain. Recombinant protein productivity by the newly constructed strain at a level of more than 1.6 g/L was attained consistently in a simple batch bioreactor. © 1994 John Wiley & Sons, Inc.
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    Extraction of rIL-2 inclusion bodies from Escherichia coli using cross-flow filtration (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 43 (1994), S. 969-977 
    Details
    ISSN: 0006-3592
    Keywords: cross-flow membrane filtration ; inclusion bodies ; Escherichia coli ; extraction, rIL-2 ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A cross-flow membrane filtration process was developed for the recovery of rIL-2 inclusion bodies from homogenized Escherichia coli. The membrane extraction process was comprised of a two-step diafiltration followed by an extraction with 7 M GuHCl and a 40-fold dilution of the solubilized inclusion bodies into 0.01 M Tris-HCl, 0.035 M NaCl, pH 7.9. The first diafiltration was with a 0.03 M Tris-HCl, 5 mM ethylenediaminetetraacetic acid (EDTA), pH 8, followed by a diafiltration with 1.75 M GuHCl. All of the insoluble rIL-2 was retained behind the membrane, whereas a GuHCl wash solubilized approximately 15% of the rIL-2. The membrane process increased the yield of rIL-2 in the diluted extract by threefold as compared to a similar centrifuge process with a significant increase in purity as determined by reverse-phase high-performance liquid chromatography (HPLC). © 1994 John Wiley & Sons, Inc.
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    Sinusoidal 60 Hz electromagnetic fields failed to induce changes in protein synthesis in Escherichia coli (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Bioelectromagnetics 15 (1994), S. 283-291 
    Details
    ISSN: 0197-8462
    Keywords: electromagnetic field ; protein synthesis ; Escherichia coli ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: Escherichia coli JM83 {F- ara Δ(lac-proAB) rpsL [φ80dΔ(lacZ)M15]} in midlog growth phase at 30 °C were exposed to 60 Hz sinusoidal magnetic field of 3 mT of nonuniform diverging flux, inducing a nonuniform electric field with a maximum intensity of 32 μV/cm using an inductor coil. Exposed and unexposed control cells were maintained at 30.8 ± 0.1 °C and 30.5 ± 0.1 °C, respectively. Quadruplicate samples of exposed and unexposed E. coli cells were simultaneously radiolabeled with 35S-L-methionine at 10 min intervals over 2 hr. Radiochemical incorporation into proteins was analyzed via liquid scintillation counting and by denaturing 12.5% polyacrylamide gel electrophoresis. The results showed that E. coli exposed to a 60 Hz magnetic field of 3 mT exhibited no qualitative or quantitative changes in protein synthesis compared to unexposed cells. Thus small prokaryotic cells (less than 2 μm × 0.5 μm) under constant-temperature conditions do not alter their protein synthesis following exposure to 60 Hz magnetic fields at levels at 3 mT. © 1994 Wiley-Liss, Inc.
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    Preparation of Diastereomeric 3,4-O-Pyruvate Acetal-Containing D-Galactopyranose Derivatives, Structural Assignment and Use for Oligosaccharide Synthesis (1994)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1994 (1994), S. 859-866 
    Details
    ISSN: 0170-2041
    Keywords: Galactosides, 3,4-pyruvylated ; Oligosaccharides ; Carbohydrates ; Escherichia coli ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Treatment of phenyl 1-thio- and allyl 2,6-di-O-benzoyl-D-galactopyranosides 3 with methyl pyruvate and BF3 · Et2O in various solvents gave 1,6-anhydro-3,4-di-O-benzoyl-2-deoxy-2-phenylthio-β-D-idopyranose (4) and the corresponding diastereomers of 3,4-O-pyruvate acetal-containing galactosides 5. The phenyl 1-thio-β-galactoside R-5a and the allyl a-galactoside R-5b were both converted into methyl 3,4-O-[1-(R)-(methoxycarbonyl)ethylidene]-β-D-galactopyranoside (9), the structure of which as well as that of 4 was confirmed by X-ray crystallography. Compound R-5a was converted into 5-[(benzyloxycarbonyl)amino]pentyl 6-O-benzoyl-3,4-O-[1-(R)-(methoxycarbonyl)ethylidene]-β-D-galactopyranoside (18) by using the (2-chloroacetoxymethyl)benzoyl (CAMB) group for the temporary protection of position 2. Glucosamination of 18 and subsequent deblocking of the intermediate disaccharide gave β-D-GlcpNAc-(1→2)-3,4-(S)-pyruvate-β-D-Galp-O(CH2)5NH2 (21) which represents a fragment of the Escherichia coli K 47 polysaccharide.
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    Detection of fundamental principles and a level of order for large-scale gene clustering on the Escherichia coli chromosome (1993)
    Springer
    Journal of molecular evolution 36 (1993), S. 347-360 
    Details
    ISSN: 1432-1432
    Keywords: Chromosome evolution ; Gene evolution ; Bacterial chromosomal expansion ; Chromosomal gene organization ; Gene clustering ; Gene duplication ; Escherichia coli ; Bacteria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The Escherichia coli K-12 genetic map was divided into intervals of equal length to count the number of genes per interval. Plots of genes per interval at four sets of interval lengths revealed large-scale clustering of genes with the major clusters occurring at regularly spaced distances apart. Major gene cluster properties were analyzed at a scale of 100 intervals wherein each interval corresponded to a genetic map unit length of 1 min. In any major gene cluster, the highest gene concentration was observed at or near the midpoint interval, and the number of genes per interval was found to decline exponentially as a function of the linear distance from the midpoint or interval of peak gene concentration of that cluster. An autocorrelation analysis of gene content in first-neighbor intervals throughout the chromosome revealed an ordered first-neighbor relationship in comparison to 2,000 randomized interval versions of the chromosome. Attempts to simulate gene placement by a Gaussian model did not produce large-scale gene clustering in any way comparable to that observed on the chromosome. We propose that major gene clusters formed from smaller gene clusters, and the contemporary chromosome formed from fusion of homologous or heterologous major gene clusters.
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    Effect of passage through the intestinal tract of detritivore earthworms (Lumbricus spp.) on the number of selected Gram-negative and total bacteria (1993)
    Springer
    Biology and fertility of soils 16 (1993), S. 227-232 
    Details
    ISSN: 1432-0789
    Keywords: Earthworms ; Lumbricus spp. ; Bacterial survival ; Enterobacter cloacae ; Escherichia coli ; Aeromonas hydrophila ; Pseudomonas putida
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Laboratory experiments were carried out to investigate the fate of bacteria during and after passage through the intestinal tract of detritivore earthworms. Earthworms (Lumbricus spp.) were fed with cattle dung inoculated 7 days previously with one of five different Gram-negative bacteria. Bacterial concentrations were determined 2 days later in dung and soil, and in gut material from different parts of the earthworm intestinal tract. A high percentage (28–82%) of the total bacteria (epifluorescence direct counts) in the earthworm gut content was culturable. The concentration of total heterotrophic aerobic bacteria did not vary significantly among the five different bacterial additions and the non-inoculated control. In earthworm casts the number of total heterotrophs per gram dry matter (2.1×109) was higher than in soil (1.7×108), but lower than in the dung (1.5×1010). The test-bacteria, however, showed different survival patterns along the earthworm intestinal tract. The concentrations of Escherichia coli BJ 18 and Pseudomonas putida MM 1 and MM 11 in earthworm casts were lower than in the ingested dung, while concentrations of Enterobacter cloacae A 107 and Aeromonas hydrophila DMU 115 in dung and casts were similar. Ent. cloacae, and to aminor extent E. coli, were reduced in numbers by several orders of magnitude in the pharynx and/or crop. In the hind gut, however, the concentration of Ent. cloacae had increased to the same level as in the ingested dung, while the concentration of E. coli remained low. Our observations indicate that the bacterial flora of ingested food materials changes qualitatively and quantitatively during gut transit.
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    Molecular organization of the Escherichia coli gab cluster: nucleotide sequence of the structural genes gabD and gabP and expression of the GABA permease gene (1993)
    Springer
    Archives of microbiology 160 (1993), S. 454-460 
    Details
    ISSN: 1432-072X
    Keywords: Succinic semialdehyde dehydrogenase ; GABA permease ; Gab cluster ; REP elements ; GABA transport ; Escherichia coli
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We have determined the nucleotide sequences of two structural genes of the Escherichia coli gab cluster, which encodes the enzymes of the 4-aminobutyrate degradation pathway: gabD, coding for succinic semialdehyde dehydrogenase (SSDH, EC 1.2.1.16) and gabP, coding for the 4-aminobutyrate (GABA) transport carrier (GABA permease). We have previously reported the nucleotide sequence of the third structural gene of the cluster, gabT, coding for glutamate: succinic semialdehyde transaminase (EC 2.6.1.19). All three gab genes are transribed unidirectionally and their orientation within the cluster is 5′-gabD-gabT-gabP-3′. gabT and gabP are separated by an intergenic region of 234-bp, which contains three repetetive extragenic palindromic (REP) sequences. The gabD gene consists of 1,449 nucleotides specifying a protein of 482 amino acids with a molecular mass of 51.7 kDa. The protein shows significant homologies to the NAD+-dependent aldehyde dehydrogenase (EC 1.2.1.3) from Aspergillus nidulans and several mammals, and to the tumor associated NADP+-dependent aldehyde dehydrogenase (EC 1.2.1.4) from rat. The permease gene gabP comprises 1,401 nucleotides coding a highly hydrophobic protein of 466 amino acids with a molecular mass of 51.1 kDa. The GABA permease shows features typical for an integral membrane protein and is highly homologous to the aromatic acid carrier from E. coli, the proline, arginine and histidine permeases from Saccharomyces cerevisiae and the proline transport protein from A. nidulans. Uptake of GABA was increased ca. 5-fold in transformants of E. coli containing gabP plasmids. Strong overexpression of the gabP gene under control of the isopropyl-2-d-thiogalactoside (IPTG) inducible tac promoter, however, resulted in a severe growth inhibition of the transformed strains. The GABA carrier was characterized using moderately overexpressing transformants. The K m of GABA uptake was found to be 11.8 μM and the Vmax 0.33 nmol/min · mg cells. Uptake of GABA was stimulated by ammonium sulfate and abolished by 2,4-dinitrophenol. Aspartate competed with GABA for uptake.
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    Effect of novel compound, 1-methyl-1-piperidino methane sulfonate (MPMS), on the osmoprotectant activity of glycine betaine, cholien and l-proline in Escherichia coli (1993)
    Springer
    Archives of microbiology 160 (1993), S. 81-86 
    Details
    ISSN: 1432-072X
    Keywords: Osmoprotectants ; Choline ; Proline ; Glycine betaine ; 1-Methyl-1-piperidino methane sulfonate (MPMS) ; Transport ; Escherichia coli
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A novel compound, 1-methyl-1-piperidino methane sulfonate (MPMS), was found to block the osmoprotectant activity of choline and L-proline, but not glycine betaine in Escherichia coli. MPMS was more active against salt-sensitive than salt-resistant strains, but had no effect on the salt tolerance of a mutant which was unable to transport choline, glycine betaine and proline. Growth of E. coli in NaCl was inhibited by MPMS and restored by glycine betaine, but not by choline or L-proline. Uptake of radiolabeled glycine betaine, choline or L-proline by cells grown at high osmolarity was not inhibited when MPMS and the radioactive substrates were added simultaneously. Preincubation for 5 min with MPMS reduced the uptake of choline and L-proline, but not glycine betaine. Similar incubation with MPMS had no effect on the uptake of radiolabeled glucose or succinate. The toxicity of MPMS was much lower than that of the L-proline analogues L-azetidine-2-carboxylic acid and 3,4-dehydro-DL-proline. The exact mechanism by which MPMS exerts its effect is not entirely clear. MPMS or a metabolite may interfere with the activity of several independent permeases involved in the uptake of osmoprotective compounds, or the conversion of choline to glycine betaine, or effect the expression of some of the osmoregulatory genes.
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    Regulation of anaerobic respiratory pathways in Wolinella succinogenes by the presence of electron acceptors (1993)
    Springer
    Archives of microbiology 159 (1993), S. 477-483 
    Details
    ISSN: 1432-072X
    Keywords: Fumarate respiration ; Nitrate respiration ; Polysulphide respiration ; Anaerobic regulation ; Wolinella succinogenes ; Escherichia coli
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In Wolinella succinogenes ATP synthesis and consequently bacterial growth can be driven by the reduction of either nitrate (E′0=+0.42 V), nitrite (E′0=+0.36 V), fumarate (E′0=+0.03 V) or sulphur (E′0=-0.27 V) with formate as the electron donor. Bacteria growing in the presence of nitrate and fumarate were found to reduce both acceptors simultaneously, while the reduction of both nitrate and fumarate is blocked during growth with sulphur. These observations were paralleled by the presence and absence of the corresponding bacterial reductase activities. Using a specific antiserum, fumarate reductase was shown to be present in bacteria grown with fumarate and nitrate, and to be nearly absent from bacteria grown in the presence of sulphur. The contents of polysulphide reductase, too, corresponded to the enzyme activities found in the bacteria. This suggests that the activities of anaerobic respiration are regulated at the biosynthetic level in W. succinogenes. Thus nitrate and fumarate reduction are repressed by the most electronegative acceptor of anacrobic respiration, sulphur. By contrast, in Escherichia coli a similar effect is exerted by the most electropositive acceptor, O2. W. succinogenes also differs from E. coli in that fumarate reductase is not repressed by nitrate.
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    Copper-containing nitrite reductase from Pseudomonas aureofaciens is functional in a mutationally cytochrome cd 1-free background (NirS−) of Pseudomonas stutzeri (1993)
    Springer
    Archives of microbiology 160 (1993), S. 18-26 
    Details
    ISSN: 1432-072X
    Keywords: Nucleotide sequence ; Apocytochrome cd 1 ; Heme d 1 incorporation ; Denitrification ; Copper coordination ; Signal peptide ; Escherichia coli
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The structural gene, nirK, for the respiratory Cu-containing nitrite reductase from denitrifying Pseudomonas aureofaciens was isolated and sequenced. It encodes a polypeptide of 363 amino acids including a signal peptide of 24 amino acids for protein export. The sequence showed 63.8% positional identity with the amino acid sequence of “Achromobacter cycloclastes” nitrite reductase. Ligands for the blue, type I Cu-binding site and for a putative type-II site were identified. The nirK gene was transferred to the mutant MK202 of P. stutzeri which lacks cytochrome cd 1 nitrite reductase due to a transposon Tn5 insertion in its structural gene, nirS. The heterologous enzyme was active in vitro and in vivo in this background and restored the mutationally interrupted denitrification pathway. Transfer of nirK to Escherichia coli resulted in an active nitrite reductase in vitro. Expression of the nirS gene from P. stutzeri in P. aureofaciens and E. coli led to nonfunctional gene products. Nitrite reductase activity of cell extract from either bacterium could be reconstituted by addition of heme d 1, indicating that both heterologous hosts synthesized a cytochrome cd 1 without the d 1-group.
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    Transient, specific and extremely rapid release of osmolytes from growing cells of Escherichia coli K-12 exposed to hypoosmotic shock (1993)
    Springer
    Archives of microbiology 160 (1993), S. 424-431 
    Details
    ISSN: 1432-072X
    Keywords: Osmoadaptation ; Hypoosmotic shock ; Stretch-activated channels ; K+ release ; Glutamate release ; Trehalose release ; K+ uptake ; Glutamate uptake ; Amino-acid pool ; Accute osmotic stress ; Escherichia coli
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The influence of hypoosmotic shock on the solute content of growing Escherichia coli K-12 cells was investigated at 37°C. Within 20 s after the shock the cells had released most of their osmolytes K+, glutamate and trehalose. This release was specific and not due to rupture of the cell membrane, since under these conditions i) the cells neither lost protein nor ATP, ii)[14C]-labeled sucrose did not enter the cytoplasm from the periplasm, and iii) except for their glutamate and aspartate level, which decreased, the amino acid pool of alanine, lysine and arginine of the cells remained approximately constant. Within a minute after the shock the cells started to reaccumulate parts of their previously released glutamate, aspartate and K+, but not trehalose and resumed growth within 10 min after the shock. Experiments with K+-transport mutants showed that none of the genetically-identified K+ transport systems is involved in the K+-release process. Reaccumulation of K+ took place via the uptake systems TrkG and TrkH. The possibility is discussed that the exit of solutes after hypoosmotic shock occurs via several stretch-activated channels, which each allow the release of a specific osmolyte.
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    Type selective inhibition of microbial fatty acid synthases by thiolactomycin (1993)
    Springer
    Archives of microbiology 160 (1993), S. 158-161 
    Details
    ISSN: 1432-072X
    Keywords: Branched-chain fatty acids ; Fatty acid synthase ; Thiolactomycin ; Selective inhibitor ; Bacillus subtilis ; Bacillus cereus ; Bacillus insolitus ; Escherichia coli
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The antibiotic, thiolactomycin, is known to selectively inhibit the Type II straight-chain fatty acid synthase (monofunctional enzyme system, e.g. Escherichia coli enzyme) but not Type I straight-chain fatty acid synthase (multifunctional enzyme system, e.g. Saccharomyces cerevisiae enzyme). We have studied the effect of thiolactomycin on the branched-chain fatty acid synthases from Bacillus subtilis, Bacillus cereus, and Bacillus insolitus. Fatty acid synthase from all three Bacilli was not inhibited or only slightly inhibited by thiolactomycin. E. coli synthase, as expected, was strongly inhibited by thiolactomycin. Branched-chain fatty acid synthase from Bacillus species is a monofunctional enzyme system but, unlike Type II E. coli synthase, it is largely insensitive to thiolactomycin.
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    The reduction of nitrous oxide to dinitrogen by Escherichia coli (1993)
    Springer
    Archives of microbiology 160 (1993), S. 432-439 
    Details
    ISSN: 1432-072X
    Keywords: Nitrous oxide reduction ; Dinitrogen formation ; Denitrification ; NOx-production ; Nitrate dissimilation ; Escherichia coli
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Escherichia coli K12 reduces nitrous oxide stoichiometrically to molecular nitrogen with rates of 1.9 μmol/h x mg protein. The activity is induced by anaerobiosis and nitrate. N2+formation from N2O is inhibited by C2H2 (K i ∼ 0.03 mM in the medium) and nitrite (K i=0.3 mM) but not by azide. A mutant defective in FNR synthesis is unable to reduce N2O to N2. The reaction in the wild type could routinely be followed by gas chromatography and alternatively by mass spectrometry measuring the formation of 15N2 from 15N2O. The enzyme catalyzing N2O-reduction in E. coli could not be identified; it is probably neither nitrate reductase nor nitrogenase. E. coli does not grow with N2O as sole respiratory electron acceptor. N2O-reduction might not have a physiological role in E. coli, and the enzyme involved might catalyze something else in nature, as it has a low affinity for the substrate N2O (apparent K m∼3.0 mM). The capability for N2O-reduction to N2 is not restricted to E. coli but is also demonstrable in Yersinia kristensenii and Buttiauxella agrestis of the Enterobacteriaceae. E. coli is able to produce NO and N2O from nitrite by nitrate reductase, depending on the assay conditions. In such experiments NO inf2 sup- is not reduced to N2 because of the high demand for N2O of N2O-reduction and the inhibitory effect of NO inf2 sup- on this reaction.
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    MKES Tools: A microbial kinetics expert system for developing and assessing food production systems (1993)
    Springer
    Journal of industrial microbiology and biotechnology 12 (1993), S. 256-262 
    Details
    ISSN: 1476-5535
    Keywords: Listeria ; Salmonella ; Shigella ; Aeromonas ; Staphylococcus ; Escherichia coli ; Bacillus cereus ; Clostridium botulinum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary MKES Tools is a microbial kinetics expert system for developing food production systems and assessing product safety. The specific information required as input are: (1) a flowchart of the production system, (2) the factors affecting the survival and growth of food-borne pathogens and (3) the ranges of variation for each factor's parameters. With this information, MKES Tools simulates the growth and survival of pathogenic microorganisms when subjected to many different factor/parameter situations. The responses obtained are then used to estimate the significance of each factor's parameters.
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    Potential for gene transfer from recombinantEscherichia coli K-12 used in bovine somatotropin production to indigenous bacteria in river water (1993)
    Springer
    Journal of industrial microbiology and biotechnology 11 (1993), S. 235-241 
    Details
    ISSN: 1476-5535
    Keywords: Gene transfer ; Escherichia coli ; River water ; Indigenous bacteria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary This study examined the transfer of the plasmid pBGH1, an expression vector for bovine somatotropin (BST), fromEscherichia coli K-12 strain W3110G [pBGH1] to indigenous microorganisms present in flasks containing Missouri River water. Strain LBB269 is a nalidixic acid-resistant derivative of W3110G which was used as a plasmid-free control strain in these studies. Water samples were inoculated with strains W3110G [pBGH1] and LBB269; after 21 days of incubation the number of viable colony-forming units (CFU) of W3110G [pBGH1] and LBB269 were reduced from an initial level of about 1×107 CFU per ml to less than 1 CFU per 100 ml. At this time indigenous microbes resistant to both ampicillin and tetracycline (the antibiotic resistance markers on pBGH1) were isolated from 100 ml of water from each of the flasks inoculated with either strain W3110G [pBGH1] or LBB269. Plasmid DNA was isolated from these organisms and examined for sequences containing the gene for BST from pBGH1, using a polymerase chain reaction (PCR) assay. As expected, the day 0 sample from the flask inoculated withE. coli K-12 strain W3110G [pBGH1] gave a positive PCR response and the day 0 sample from the flask inoculated withE. coli K-12 strain LBB269 gave a negative PCR response. All of the day 21 samples containing indigenous microbes isolated from flasks that were inoculated with either W3110G [pBGH1] or LBB269 were negative in the PCR assay, indicating that the target sequence from pBGH1 was not present in any of these indigenous microorganisms. The results of this particular assay indicate that pBGH1 or the portion of pBGH1 including the BST structural gene had not been transferred from W3110G [pBGH1] to indigenous microbial inhabitants of the Missouri River water flasks during this study.
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    Altered topoisomerase activities may be involved in the regulation of DNA supercoiling in aerobic-anaerobic transitions inEscherichia coli (1993)
    Springer
    Molecular and cellular biochemistry 126 (1993), S. 115-124 
    Details
    ISSN: 1573-4919
    Keywords: DNA supercoiling ; DNA topoisomerases ; [ATP]/[ADP] ratio ; aerobic anaerobic transitions ; Escherichia coli
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract This study uncovers a new mechanism of regulation of DNA supercoiling operativein vivo upon an aerobic-anaerobic transition inEscherichia coli. Exponentially growing aerobic batch cultures were subjected to a shift to anaerobic conditions. The ratio [ATP]/[ADP] remained essentially constant at 8.5 in the aerobic culture and after a transition to anaerobiosis while DNA supercoiling increased noticeably upon anaerobiosis. This result indicated that the mechanism of regulation of DNA supercoiling by the [ATP]/[ADP] ratio was not operative. The increase in DNA supercoiling was followed by a large decrease in the DNA-relaxing activity of topoisomerase I while gyrase activity remained relatively constant. This decrease in the activity of topoisomerase I is likely to be responsible for the increase in DNA supercoiling.
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    Expression of cGMP-dependent protein kinase inEscherichia coli (1993)
    Springer
    Molecular and cellular biochemistry 127-128 (1993), S. 71-80 
    Details
    ISSN: 1573-4919
    Keywords: Cyclic GMP-dependent protein kinase ; Escherichia coli ; post-translational modification ; protein folding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Cyclic GMP-dependent protein kinase (cGMP kinase) is involved in the relaxation of smooth muscle. The enzyme has been cloned and expressed in eukaryotic cell lines but so far not in prokaryotic cells. Three vectors were constructed for the expression of Iα cGMP kinase inEscherichia coli. Transformation with the pET3a/cgk vector which uses the T7 RNA polymerase/promotor system resulted in efficient accumulation of cGMP kinase. Most of the protein was in an insoluble and catalytic inactive form. Various solubilization and refolding conditions did not yield an active enzyme. A small fraction of the cGMP kinase was present in the soluble cell extract. This fraction bound cGMP with high affinity but had no cGMP stimulated kinase activity. To prevent aggregation two additional vectors were constructed. (I) A bacterial leader sequence, which directs the export of proteins into the periplasmic space, was fused to the aminoterminus of the cGMP kinase. (II) A gram/gram+ shuttle vector for expression under the control of the tac promotor was used. Both constructs directed the synthesis of an isoluble and inactive cGMP kinase. These results suggest that large amounts of cGMP kinase can be expressed inE. coli, but mainly in an isoluble and inactive form. In contrast to eukaryotic cells, bacteria may lack systems for correct protein folding and/or posttranslational modification that are crucial for the productive folding and/or activation of cGMP kinase.
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    Polypyrimidine/polypurine sequence in plasmid DNA enhances formation of dimer molecules inEscherichia coli (1993)
    Springer
    Molecular biology reports 18 (1993), S. 183-187 
    Details
    ISSN: 1573-4978
    Keywords: DNA triple helix ; Escherichia coli ; plasmid DNA ; polypyrimidine/polypurine bias ; recombination ; replication
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Formation of dimer molecules of a recombinant plasmid, pTIR10, which carries a pyrimidine/purine-biased stretch occurs about 6-fold more efficiently than for the control plasmid pUC19 inEscherichia coli strain JM107. Since pyrimidine/purine-biased sequences have a potential to form unusual DNA structures, this observation suggests that the inserted sequence affects the replication process of plasmid DNA, probably by forming a triple helix under physiological conditions.
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    Characterization of pea chloroplastic carbonic anhydrase. Expression inEscherichia coli and site-directed mutagenesis (1993)
    Springer
    Plant molecular biology 22 (1993), S. 937-943 
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    ISSN: 1573-5028
    Keywords: carbonic anhydrase ; Escherichia coli ; mutagenesis ; Pisum sativum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A cDNA encoding the mature, chloroplast-localized carbonic anhydrase in pea has been expressed inE. coli. The enzyme is fully active and yields of up to 20% of the total soluble protein can be obtained from the bacteria. This expression system was used to monitor the effects of site-directed mutagenesis of seven residues found within conserved regions in the pea carbonic anhydrase amino acid sequence. The effects of these modifications are discussed with respect to the potential of various amino acids to act as sites for zinc coordination or intramolecular proton shuttles.
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    Cloning, sequence analysis and expression of a cDNA encoding active phosphoenolpyruvate carboxylase of the C3 plant Solanum tuberosum (1993)
    Springer
    Plant molecular biology 23 (1993), S. 881-888 
    Details
    ISSN: 1573-5028
    Keywords: cDNA ; complementation ; C3 plant ; Escherichia coli ; phosphoenolpyruvate carboxylase ; Solanum tuberosum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A cDNA coding for phosphoenolpyruvate carboxylase (PEPC) was isolated from a cDNA library from Solanum tuberosum and the sequence of the cDNA was determined. It was inserted into a bacterial expression vector and a PEPC- Escherichia coli mutant could be complemented by the cDNA construct. A functional fusion protein could be synthesized in E. coli. The properties of this PEPC protein clearly resembled those of typical C3 plant enzymes.
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    Voltage-dependent cationic channel of Escherichia coli (1993)
    Springer
    The journal of membrane biology 133 (1993), S. 119-127 
    Details
    ISSN: 1432-1424
    Keywords: bacteria ; Escherichia coli ; ion channel ; porin ; patch clamp ; liposomes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary A fraction highly enriched with inner membranes of E. coli was fused with liposomes, using the dehydration-rehydration technique, to produce giant liposomes amenable to patch-clamp recordings. Among the several channels present in this type of preparation, one was further characterized. The channel has a conductance of some 200 pS (in 0.1 m KCl) and is weakly selective for cations (PK/PCl = 4). The channel stays open at negative and low positive membrane potentials and shows an increasing probability of closure with increasing voltage. High positive membrane potentials favor transitions to a long-lived inactivated state, following slow kinetics. Voltage-dependent rapid flickerings of the same amplitude, between open state and other short-lived closed states, are superposed on these kinetics. The channel is presumed to be localized in the inner membrane, but its characteristics are also compatible with those of porins of the outer membrane. However, the major porins OmpF and OmpC, purified and reconstituted into giant liposomes, exhibited a marked different behavior.
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    Domains of colicin M involved in uptake and activity (1993)
    Springer
    Molecular genetics and genomics 240 (1993), S. 103-112 
    Details
    ISSN: 1617-4623
    Keywords: Colicin M uptake ; TonB box activity ; Escherichia coli
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Colicin M inhibits murein biosynthesis by interfering with bactoprenyl phosphate carrier regeneration. It belongs to the group B colicins the uptake of which through the outer membrane depends on the Tong, ExbB and ExbD proteins. These colicins contain a sequence, called the Tong box, which has been implicated in transport via Tong. Point mutations were introduced by PCR into the TonB box of the structural gene for colicin M, cma, resulting in derivatives that no longer killed cells. Mutations in the tonB gene suppressed, in an allele-specific manner, some of the cma mutations, suggesting that interaction of colicin M with Tong may be required for colicin M uptake. Among the hydroxylamine-generated colicin M-inactive cma mutants was one which carried cysteine in place of arginine at position 115. This Colicin derivative still bound to the FhuA receptor and killed cells when translocated across the outer membrane by osmotic shock treatment. It apparently represents a new type of transport-deficient colicin M. Additional hydroxylamine-generated inactive derivatives of colicin M carried mutations centered on residues 193–197 and 223–252. Since these did not kill osmotically shocked cells the mutations must be located in a region which is important for colicin M activity. It is concluded that the Tong box at the N-terminal end of colicin M must be involved in colicin uptake via Tong across the outer membrane and that the C-terminal portion of the molecule is likely to contain the activity domain.
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    A technique for targeted mutagenesis of the EF-Tu chromosomal gene by M13-mediated gene replacement (1993)
    Springer
    Molecular genetics and genomics 238 (1993), S. 252-260 
    Details
    ISSN: 1617-4623
    Keywords: EF-Tu ; Targeted mutagenesis ; Mapping ; M13 phage ; Kirromycin ; Escherichia coli
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A generally applicable system for targeted mutagenesis of a chromosomal sequence is described. The Escherichia coli tufA gene was mutated using a recombinant M13mp9 phage vector carrying a tuf gene. Integration via crossing over with the chromosomal tufA target gene produced an M13 lysogen. These lysogens were screened for resistance to kirromycin. The M13 phage carrying tufA mutations were efficiently retrieved by a genetic procedure. Genetic mapping was performed with the M13 vectors. The same recombinant M13 phage was used for mutagenesis, lysogen formation, gene replacement, retrieval, mapping and sequencing of kirromycin mutants. Three different mutations yielding resistance to kirromycin were found: two of these have previously been found and characterised, while the third mutation, Gly316 → Asp, is a new mutant. We also report the identification of a fourth kirromycin-resistant mutant, Gln124 → Lys.
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    Specific chromosomal sites enhancing homologous recombination in Escherichia coli mutants defective in RNase H (1993)
    Springer
    Molecular genetics and genomics 240 (1993), S. 307-314 
    Details
    ISSN: 1617-4623
    Keywords: RNase H ; Recombinational hotspot ; Chi activity ; Replication termination region ; Escherichia coli
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract To clone new replication origin(s) activated under RNase H-defective (rnh −) conditions in Escherichia coli cells, whole chromosomal DNA digested with EcoRI was to with a Kmr DNA fragment and transformed into an rnh− derivative host. From the Kmr transformants, we obtained eight kinds of plasmid-like DNA, each of which contained a specific DNA fragment, termed “Hot”, derived from the E. coli genome. Seven of the Hot DNAs (HotA-G) mapped to various sites within a narrow DNA replication termination region (about 280 kb), without any particular selection. Because Hot DNA could not be transformed into a mutant strain in which the corresponding Hot region had been deleted from the chromosome, the Hot DNA, though obtained as covalently closed circular (ccc) DNA, must have arisen by excision from the host chromosome into which it had initially integrated, rather than by autonomous replication of the transformed species. While Hot DNA does not have a weak replication origin it does have a strong recombinational hotspot active in the absence of RNase H. This notion is supported by the finding that Chi activity was present on all Hot DNAs tested and no Hot-positive clone without Chi activity was obtained, with the exception of a DNA clone carrying the dif site.
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    AICAR is not an endogenous mutagen in Escherichia coli (1993)
    Springer
    Molecular genetics and genomics 240 (1993), S. 355-359 
    Details
    ISSN: 1617-4623
    Keywords: AICAR ; Substitution mutations ; Spontaneous mutagenesis ; Escherichia coli
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A number of observations in the Escherichia coli and Salmonella typhimurium literature could be explained by the hypothesis that a particular purine ribonucleotide precursor can be converted to the corresponding deoxyribonucleotide triphosphate, thereby becoming a base-analogue mutagen. The metabolite in question, AICAR (5-amino-4-carboxamide imidazole riboside 5′-phosphate), is also a by-product of histidine biosynthesis, and its (ribo)triphosphate derivative, ZTP, has been detected in E. coli. We constructed E. coli tester strains that had either a normal AICAR pool (pur + his + strains cultivated without purines or histidine) or no AICAR pool (purF hisG mutant strains, lacking the first enzyme of each pathway and cultivated in the presence of adenine and histidine). Using a set of lacZ mutations, each of which can revert to Lac+ only by a specific substitution mutation, we found that no base substitution event occurs at a higher frequency in the presence of an AICAR pool. We conclude that the normal AICAR pool in E. coli is not a significant source of spontaneous base substitution mutagenesis.
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    Cloning and mapping of the genetic determinants for microcin C51 production and immunity (1993)
    Springer
    Molecular genetics and genomics 241 (1993), S. 700-706 
    Details
    ISSN: 1617-4623
    Keywords: Microcin C51 ; Peptide antibiotic ; Plasmid genes ; Escherichia coli
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Microcin C51 is a small peptide antibiotic produced by Escherichia coli cells harbouring the 38 kb low copy number plasmid pC51, which codes for microcin production and immunity. The genetic determinants for microcin synthesis and immunity were cloned into the vectors pBR325, pUC19 and pACYC184. Physical and phenotypic analysis of deletion derivatives and mutant plasmids bearing insertions of transposon Tn5 showed that a DNA fragment of about 5 kb is required for microcin C51 synthesis and expression of complete immunity to microcin. Partial immunity can be provided by a 2 kb DNA fragment. Mutant plasmids were tested for their ability to complement Mic− mutations. Results of these experiments indicate that at least three plasmid genes are required for microcin production. The host OmpR function is also necessary for microcin C51 synthesis.
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    LamB as a carrier molecule for the functional exposition of IgG-binding domains of the Staphylococcus aureus Protein A at the surface of Escherichia coli K12 (1993)
    Springer
    Molecular genetics and genomics 236 (1993), S. 187-192 
    Details
    ISSN: 1617-4623
    Keywords: LamB ; Staphylococcal protein A ; Surface expression ; IgG binding ; Escherichia coli
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary One, two or four IgG-binding domains of the Staphylococcus aureus Protein A (SPA) were inserted into the LamB protein which was expressed under control of the tac promoter. The chimeric proteins were shown to be exposed at the cell surface by analysis of isolated outer membranes and also by testing their functional interaction with IgG molecules. We hereby show that the LamB protein can accept as many as 232 amino acids (four SPA domains) and still be incorporated into the Escherichia coli outer membrane, while maintaining the functional conformation of the inserted SPA polypeptides.
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    TdcA, a transcriptional activator of the tdcABC operon of Escherichia coli, is a member of the LysR family of proteins (1993)
    Springer
    Molecular genetics and genomics 240 (1993), S. 395-402 
    Details
    ISSN: 1617-4623
    Keywords: Escherichia coli ; tdc operon ; tdc activator ; Gene regulation ; LysR family of proteins
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The tdcB and tdcC genes of the tdcABC operon of Escherichia coli encode threonine dehydratase and a threonine-serine permease, respectively. These proteins are involved in transport and metabolism of threonine and serine during anaerobic growth. In this study, we functionally characterized tdcA, which encodes a 35 kDa polypeptide consisting of 312 amino acid residues. Non-polar and partially polar mutations introduced into tdcA drastically reduced the expression of the genes down-stream from tdcA. Complementation studies using single-copy chromosomal integrants of a tdcB-lacZ fusion harboring an in-frame deletion of tdcA with chromosomal or plasmid-borne tdcA + in trans showed complete restoration of tdc operon expression in vivo. The amino acid sequene at the amino-terminal end of TdcA revealed a significant homology to the helix-turn-helix motifs of typical DNA binding proteins. Sequence alignment of TdcA with LysR also showed considerable sequence similarity throughout their entire lengths. Our results suggest that TdcA is related to the LysR family of proteins by common ancestry and, based on its functional role in tdc expression, belongs to the LysR family of transcriptional activators.
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    Oligomerization of Escherichia coli haemolysin (HlyA) is involved in pore formation (1993)
    Springer
    Molecular genetics and genomics 241 (1993), S. 89-96 
    Details
    ISSN: 1617-4623
    Keywords: Haemolysin ; Escherichia coli ; Oligomerization of HlyA ; Pore formation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Coexpression of pairs of nonhaemolytic H1yA mutants in the recombination-deficient (recA) strain Escherichia coli HB101 resulted in a partial reconstitution of haemolytic activity, indicating that the mutation in one H1yA molecule can be complemented by the corresponding wild-type sequence in the other mutant HlyA molecule and vice versa. This suggests that two or more HlyA molecules aggregate prior to pore formation. Partial reconstitution of the haemolytic activity was obtained by the combined expression of a nonhaemolytic HlyA derivative containing a deletion of five repeat units in the repeat domain and several nonhaemolytic HlyA mutants affected in the pore-forming hydrophobic region. The simultaneous expression of two inactive mutant HlyA proteins affected in the region at which HlyA is covalently modified by HlyC and the repeat domain, respectively, resulted in a haemolytic phenotype on blood agar plates comparable to that of wild-type haemolysin. However, complementation was not possible between pairs of HlyA molecules containing site-directed mutations in the hydrophobic region and the modification region, respectively. In addition, no complementation was observed between HlyA mutants with specific mutations at different sites of the same functional domain, i.e. within the hydrophobic region, the modification region or the repeat domain. The aggregation of the HlyA molecules appears to take place after secretion, since no extracellular haemolytic activity was detected when a truncated but active HlyA lacking the C-terminal secretion sequence was expressed together with a non-haemolytic but transport-competent HlyA mutant containing a deletion in the repeat domain.
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    Cloning and expression of the manganese superoxide dismutase gene of Escherichia coli in Lactococcus lactis and Lactobacillus gasseri (1993)
    Springer
    Molecular genetics and genomics 239 (1993), S. 33-40 
    Details
    ISSN: 1617-4623
    Keywords: Escherichia coli ; Superoxide dismutase ; Fusion protein ; Lactococcus ; Lactobacillus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The Escherichia coli sodA gene encoding the antioxidant enzyme Mn-containing superoxide dismutase (MnSOD), was cloned in the expression vector pMG36e. This vector has a multiple cloning site down-stream of a promoter and Shine-Dalgarno sequences derived from Lactococcus. The protein-coding region of sodA from E. coli was amplified by the polymerase chain reaction, using a thermocycler and Taq DNA polymerase before cloning into pMG36e. When introduced into E. coli, the recombinant plasmid expressed the predicted fusion protein, both in the presence and absence of oxygen. The expression of the fusion protein in E. coli was verified by SOD assays, activity gels and Western blots. The recombinant plasmid was also introduced into Lactococcus lactis, which contains a resident SOD, and into Lactobacillus gasseri, which is devoid of SOD. Transformed lactococci expressed an active SodA fusion protein plus an active hybrid protein composed of subunits of the Lactococcus and the recombinant E. coli enzymes. Transformants of L. gasseri expressed only the fusion SodA protein, which was enzymatically active.
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    Attempts to define distinct parts of NADH: Ubiquinone oxidoreductase (complex I) (1993)
    Springer
    Journal of bioenergetics and biomembranes 25 (1993), S. 331-337 
    Details
    ISSN: 1573-6881
    Keywords: NADH:ubiquinone oxidoreductase ; complex I ; iron-sulfur cluster ; assembly ; gene disruption ; Neurospora crassa ; Escherichia coli
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract The NADH:ubiquinone oxidoreductase (complex I) is made up of a peripheral part and a membrane part. The two parts are arranged perpendicular to each other and give the complex an unusual L-shaped structure. The peripheral part protrudes into the matrix space and constitutes the proximal segment of the electron pathway with the NADH-binding site, the FMN and at least three iron-sulfur clusters. The membrane part constitutes the distal segment of the electron pathway with at least one iron-sulfur cluster and the ubiquinone-binding site. Both parts are assembled separately and relationships of the major structural modules of the two parts with different bacterial enzymes suggest, that both parts also emerged independently in evolution. This assumption is further supported by the conserved order of bacterial complex I genes, which correlates with the topological arrangement of the corresponding subunits in the two parts of complex I.
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    Bacterial NADH-quinone oxidoreductases: Iron-sulfur clusters and related problems (1993)
    Springer
    Journal of bioenergetics and biomembranes 25 (1993), S. 347-356 
    Details
    ISSN: 1573-6881
    Keywords: NADH-quinone oxidoreductase: NDH-1 ; iron-sulfur cluster ; Paracoccus denitrificans ; Rhodobacter sphaeroides ; Escherichia coli ; Thermus thermophilus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract Many bacteria contain proton-translocating membrane-bound NADH-quinone oxidoreductases (NDH-1), which demonstrate significant genetic, spectral, and kinetic similarity with their mitochondrial counterparts. This review is devoted to the comparative aspects of the ironsulfur cluster composition of NDH-1 from the most well-studied bacterial systems to date.:Paracoccus denitrificans, Rhodobacter sphaeroides, Escherichia coli, andThermus thermophilus. These bacterial systems provide useful models for the study of coupling Site I and contain all the essential parts of the electron-transfer and proton-translocating machinery of their eukaryotic counterparts.
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    Escherichia coli K12 does not colonize the gastrointestinal tract of Fischer-344 rats (1993)
    Springer
    Journal of industrial microbiology and biotechnology 11 (1993), S. 253-257 
    Details
    ISSN: 1476-5535
    Keywords: Colonization ; Escherichia coli ; Gastrointestinal ; Environmental ; Survival
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary The colonizing potential ofEscherichia coli K12 containing a vector coding for somidobove (bovine somatotropin) was determined. Treated male and female Fischer-344 rats were given a single oral gavage inoculum of sucrose with/without tetracycline (15 μg/ml). Untreated control animals received similar drinking water regimes. All animals survived until termination. There were no clinical signs of toxicity observed and no treatment-related effect upon body weight, food consumption, or efficiency of food utilization. Fresh fecal samples were collected from each rat every 24 h following inoculation and the population of the marked strain was quantitated until no bacterial colonies were observed for two consecutive days. While all inoculated rats were positive at 24 h, by 72 and 96 h all had become negative for the test (marked) strain, as were the corresponding control group throughout the test. The frozen stock of the marked strain used as the positive control demonstrated that the agar plates were selective for the test strain. Fourteen days following inoculation, all groups of rats were killed and the gastrointestinal tracts removed and treated to recover the marked strain. There was no evidence of the marked strain in the gastrointestinal tract of any rat from any group. Thus, theE. coli K12 host/vector system used in this experiment does not colonize the gastrointestinal tract of Fischer-344 rats.
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    URL: http://dx.doi.org/10.1007/BF01569598
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    Distribution of F-specific bacteriophages and coliphages in wastewater (1993)
    Springer
    World journal of microbiology and biotechnology 9 (1993), S. 34-36 
    Details
    ISSN: 1573-0972
    Keywords: Bacteriophages ; Escherichia coli ; Salmonella ; sewage ; wastewater
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract A new method for quantifying F-specific bacteriophages in wastewater is described. Somatic coliphages were also determined. Host-strainSalmonella typhimurium WG 49 was sensitive to only a few bacteriophages and this could have arisen from infection by F-RNA phages. Host-strainEscherichia coli ATCC 9723 C, however, supported multiplication of a wide range of bacteriophages present in sewage, giving plaque counts one to three orders of magnitude greater than those on F+ and F- salmonellas.
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    URL: http://dx.doi.org/10.1007/BF00656512
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    Incidence of multiple antibiotic resistant Escherichia coli in the Bhavani River (1993)
    Springer
    World journal of microbiology and biotechnology 9 (1993), S. 609-610 
    Details
    ISSN: 1573-0972
    Keywords: Antibiotics ; Escherichia coli ; resistance ; river water
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Of 107 Escherichia coli strains isolated from the water, sediment and fish of the Bhavani River, all of which are considered potential causes of human enteric disease, 62% were resistant to more than four antibiotics. Levels of resistance to bacitracin, penicillin, and novobiocin were generally high whereas those to polymyxin-B and chloramphenicol were much lower. A high incidence of multiple antibiotic resistant E. coli was noted in all samples and the multiple antibiotic resistance index of the strains showed that 95% of the strains originated either from man or cattle.
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    URL: http://dx.doi.org/10.1007/BF00386309
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    Kinetics of microbial growth with mixtures of carbon sources (1993)
    Springer
    Antonie van Leeuwenhoek 63 (1993), S. 289-298 
    Details
    ISSN: 1572-9699
    Keywords: carbon limitation ; chemostat ; Escherichia coli ; galactose ; glucose ; growth kinetics ; mixed substrates ; residual substrate concentration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Several investigations have shown that during growth in carbon-limited chemostats the simultaneous utilisation of carbon substrates which usually provoke diauxie under batch conditions, i.e., ‘mixed substrate growth’, is probably the rule under ecologically relevant growth conditions. In contrast, the models presently available for the description of the kinetics of microbial growth are all based on the use of single substrates. Systematic studies in chemostat culture have shown that steady-state residual concentrations of individual compounds were consistently lower during mixed substrate growth than during growth with the single substrates. This effect is clearly demonstrated for the case ofEscherichia coli growing with mixtures of glucose plus galactose. The data presented indicate that the extent of reduction of steady-state residual substrate concentration is dependent on the proportions of the substrates in the mixture, the nature of substrates mixed and the regulation pattern of enzymes involved in their breakdown. If this behaviour can be shown to be typical for growth under environmental conditions, it may provide an explanation why microbes still grow relatively fast at the low substrate concentrations encountered in nature.
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    URL: http://dx.doi.org/10.1007/BF00871224
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    Relieving effects of glycine and methionine from acetic acid inhibition in Escherichia coli fermentation (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 41 (1993), S. 316-324 
    Details
    ISSN: 0006-3592
    Keywords: Escherichia coli ; acetic acid ; inhibition ; glycine ; methionine ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Among amino acids screened for their potential to relieve wild and recombinant Escherichia coli from the negative effects of acetic acid, glycine, and methionine showed a sparing effect. In the presence of 2 g/L of acetic acid, addition of 0.5 g/L of glycine or methionine resulted in either a complete recovery or a further enhancement in the specific growth rate, while the enhancement was significant but not fully complete in the presence of 4 g/L of acetic acid. The addition of 0.5 g/L of methionine alleviated the negative effect of acetic acid on recombinant E. Coli growth to produce more β-lactamase, which was encoded by plasmid pUC18. In continuous fermentation the methionine effect on recombinant. E. coli metabolism depended on dilution rate; at high dilution rates, above 0.4 h-1, the methionine addition enhanced β-lactamase production and reduced acetic acid formation, while at low dilution rates, below 0.3 h -1, the effect was reversed. In def-batch fermentation with wild-type E. Coli, cell growth rate and cell yield from glucose were enhanced with methionine addition, while the acetic acid concentration reached over 4 g/L. © 1993 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
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    In situ fermentation monitoring with recombinant firefly luciferase (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 42 (1993), S. 30-36 
    Details
    ISSN: 0006-3592
    Keywords: Escherichia coli ; fiber optic ; firefly luciferase ; on-line ; viability ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A novel method is described for the on-line determination of viable cell number. It has been tested in fermentations of Escherichia coli. The cells are transfected with the gene for firefly luciferase and fed low levels of luciferin in the medium. The reaction requires ATP, so the nonviable cells cannot produce light. Thus, light production is linear with viable cell density from innoculation through most of exponential growth. The light emitted by these cells is then conducted from the reaction vessel to the light detection equipment by an optical fiber. With the equipment described below, as few as a 106 cells/mL, or an OD600 of 0.004, are easily detectable and concentrations greater than 1010 cells/mL are well within range. The data are collected by a computer, so adaptation to on-line control applications is straightforward. During lag phase, this method is much more accurate then optical density measurements. At the end of exponential growth, rapid changes in light production mark carbon source depletion and the onset of cell lysis. A simple model accounts for the luciferin used during the fermentation and corrects the light detected to the proper cell density. © 1993 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/bit.260420105
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    Biochemical production capabilities of escherichia coli (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 42 (1993), S. 59-73 
    Details
    ISSN: 0006-3592
    Keywords: Escherichia coli ; amino acids ; nucleotides ; biosynthesis ; linear optimization ; metabolic fluxes ; metabolic engineering ; stoichiometry ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Microbial metabolism provides at mechanism for the conversion of substrates into useful biochemicals. Utilization of microbes in industrial processes requires a modification of their natural metabolism in order to increase the efficiency of the desired conversion. Redirection of metabolic fluxes forms the basis of the newly defined field of metabolic engineering. In this study we use a flux balance based approach to study the biosynthesis of the 20 amino acids and 4 nucleotides as biochemical products. These amino acids and nucleotides are primary products of biosynthesis as well as important industrial products and precursors for the production of other biochemicals. The biosynthetic reactions of the bacterium Escherichia coli have been formulated into a metabolic network, and growth has been defined as a balanced drain on the metabolite pools corresponding to the cellular composition. Theoretical limits on the conversion of glucose, glycerol, and acetate substrates to biomass as well as the biochemical products have been computed. The substrate that results in the maximal carbon conversion to a particular product is identified. Criteria have been developed to identify metabolic constraints in the optimal solutions. The constraints of stoichiometry, energy, and redox have been determined in the conversions of glucose, glycerol, and acetate substrates into the biochemicals. Flux distributions corresponding to the maximal production of the biochemicals are presented. The goals of metabolic engineering are the optimal redirection of fluxes from generating biomass toward producing the desired biochemical. Optimal biomass generation is shown to decrease in a piecewise linear manner with increasing product formation. In some cases, synergy is observed between biochemical production and growth, leading to an increased overall carbon conversion. Balanced growth and product formation are important in a bioprocess, particularly for nonsecreted products. © 1993 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/bit.260420109
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    Defined media optimization for growth of recombinant Escherichia coli X90 (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 41 (1993), S. 221-230 
    Details
    ISSN: 0006-3592
    Keywords: Escherichia coli ; medium optimization ; chemostat ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An optimized, defined minimal medium was developed to support balanced growth of Escherichia coli X90 harboring a recombinant plasmid. Foreign protein expression was repressed in these studies. A pulse injection technique was used to identify the growth responses to nutrients in a chemostat. Once the nutrients essential for growth had been identified, the yield coefficients for individual medium components. These yield coefficients were used to develop an optimized, glucose-limited defined minimal medium that supports balanced cell growth in chemostat culture. The biomass and substrate concentrations follow the Monod chemostat model. The maximum specific growth rate determined in a washout experiment is 0.87 h-1 for this strain in the optimized medium. the glucose yield factor is 0.42 g DCW/g glucose and the maintenance coefficient is zero in the glucose-limited chemostat culture. © 1993 John Wiley & Sons, Inc.
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    URL: http://dx.doi.org/10.1002/bit.260410208
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    Isolation, renaturation, and formation of disulfide bonds of eukaryotic proteins expressed in Escherichia coli as inclusion bodies (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 41 (1993), S. 3-13 
    Details
    ISSN: 0006-3592
    Keywords: recombinant protein ; Escherichia coli ; inclusion body ; renaturation ; disulfide bond ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Expression of recombinant proteins in Escherichia coli often results in the formation of insoluble inclusion bodies, In case of expression of eukaryotic proteins containing cysteine, which may form disulfide bonds in the native active protein, often nonnative inter- and intramolecular disulfide bonds exist in the inclusion bodies. Hence, several methods have been developed to isolate recombinant eukaryotic polypeptides from inclusion bodies, and to generate native disulfide bonds, to get active proteins. This article summarizes the different steps and methods of isolation and renaturation of eukaryotic proteins containing disulfide bonds, which have been expressed in E. coli as inclusion bodies, and shows which methods originally developed for studying the folding mechanism of naturally occurring proteins have been successfully adapted for reactivation of recombinant eukaryotic proteins. © 1993 John Wiley & Sons, Inc.
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    URL: http://dx.doi.org/10.1002/bit.260410103
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    Production of the siderophore enterobactin: Use of four different fermentation systems and identification of the compound by HPLC (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 41 (1993), S. 237-244 
    Details
    ISSN: 0006-3592
    Keywords: Escherichia coli ; iron transport ; enterobactin HPLC ; dialysis membrane fermentor ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The article describes four different fermentation procedures for Escherichia coli AN311, a producer of enterobactin. A regular rotary shaker culture with a biphasic system consisting of an agar layer (as a reservoir for feeding processes) and a layer of liquid medium, 2.4 L and 10 L batch cultures, and a novel dialysis membrane fermentor were used. With the use of this latter fermentor type, the production of enterobactin could be increased by a factor of about 9.5, while growth increased by a factor of 12 compared to the other systems. For the rapid and reliable quantification of the concentration and purity of enterobactin an analytical and preparative high-performance liquid chromatography (HPLC) method was established. The degradation compounds of this siderophore were detected by diodearray and bioassays. A comparison of total catechol production as well as the distribution between enterobactin and its degradation compounds is given. © 1993 John Wiley & Sons, Inc.
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    Variation and modeling of the probability of plasmid loss as a function of growth rate of plasmid-bearing cells of Escherichia coli during continuous cultures (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 41 (1993), S. 395-404 
    Details
    ISSN: 0006-3592
    Keywords: recombinant bacterium ; plasmid loss ; modeling ; Escherichia coli ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A large number of models concerning cultures of genetically engineered bacteria have been described. Among them, some are specifically adapted to continuous cultures and lead to the determination of two variables: (i) the difference in the specific growth rates between plasmid-carrying cell and plasmid-free cells (δμ) and (ii) the frequency of plasmid loss by plasmid-containing cells (prμ+). Until now, studies have been performed on the global expression prμ+ and δμ, whose value during continuous assays have been supposed approximately constant (mean value) and not on separate values of both terms pr and μ+, respectively, probability of plasmid loss and specific growth rate of the plasmid-carrying cells. So far these studies do not allow examination of the relationship between these two last parameters. Experimental results were obtained with Escherichia coli C600 galk (GAPDH), a genetically engineered strain that synthetizes an elevated quantity of glyceraldehyde-3-phosphate dehydrogenase (GAPDH). From data obtained during continuous cultures, it is shown that during an assay, δμ, and prμ+ do not remain constant. An appropriate mathematical analysis of the expression of μ- (specific growth rate of the plasmid-free cells) and μ+ has been built up. This allows the evaluation of the values of μ+ and μ- during the continuous cultures carried out at different dilution rates. Values of pr have been calculated from these data. Indeed our results show that pr increases with μ+. A modeling approach which allows correct simulation of this variation is also proposed. This model is derived from the Hill equation regarding cooperative binding of enzymic type reaction. © 1993 John Wiley & Sons, Inc.
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    Effect of oxygen fluctuations on recombinant Escherichia coli fermentation (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 41 (1993), S. 666-670 
    Details
    ISSN: 0006-3592
    Keywords: oxygen fluctuations ; plasmid amplification ; Escherichia coli ; circulation time distribution ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Escherichia coli DH5α, carrying the pUC19 plasmid for the lacZ fragment of β-galactosidase and ampicillin resistance, was grown in a batch fermentor under conditions of fluctuating oxygen supply. A Monte Carlo method was used to control the on/off supply of air to simulate circulation of cells in a large fermentor. Rapid changes in oxygen supply reduced the rates of oxygen uptake the carbon dioxide release and prolonged the active second growth phase in batch culture, compared to growth with continuous aeration. Amplification of the plasmid was observed during the stationary phase when air supplied continuously, but not during the Monte Carlo experiments. © 1993 John Wiley & Sons, Inc.
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    Continuous, high level production and excretion of a plasmid-encoded protein by Escherichia coli in a two-stage chemostat (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 41 (1993), S. 937-946 
    Details
    ISSN: 0006-3592
    Keywords: protein excretion ; continuous culture ; Escherichia coli ; β-lactamase ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The stable continuous overproduction of a plasmidencoded protein, β-lactamase, for at least 50 days by Escherichia coli K-12, RB791(pKN), with release into the culture medium has been demonstrated in two-stage chemostats. The second-stage culture was continuously induced with 0.1 mM IPTG. Continuous expression of β-lactamase could not be sustained with this strain in a single-stage chemostat because of cell death and selection for lac-1 cells. β-Lactamase production in the second stage was sensitive to the second-stage dilution rate and the distribution of the limiting substrate (i.e., glucose) between the first and second stages. The fraction of viable, excreting cells and the average copy number in the induced culture was measurably higher under those conditions of dilution rate and substrate distribution which yielded high β-lactamase levels. The best operating conditions found at 20°C were a first-stage dilution rate of 0.12 h-1, a second-stage dilution rate of 0.03 h-1, and equal glucose feed supplied to each stage. Enzymatically active β-lactamase was produced at a level of 25% of total cellular protein with 90% excretion yielding 300 mg β-lactamase/L that was 50% pure at an OD600 〈 6. © 1993 Wiley & Sons, Inc.
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    Observations of aerobic, growing escherichia coli metabolism using an on-line nuclear magnetic resonance spectroscopy system (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 42 (1993), S. 215-221 
    Details
    ISSN: 0006-3592
    Keywords: on-line NMR ; phosphorus-31 NMR ; Escherichia coli ; aerobic and anaerobic metabolism ; intracellular pH ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An experimental system has been constructed which enables on-line measurements of phosphorus-31 (31P) nuclear magnetic resonance (NMR) spectra for growing bacterial suspensions under anaerobic or aerobic conditions. A sample stream from a laboratory bioreactor is circulated to the NMR sample chamber in a gas exchange system which permits maintenance of aerobic conditions for high-cell-density cultures. 31P NMR spectra with resolution comparable with those obtained traditionally using dense, concentrated, nongrowing cell suspensions can be obtained at cell densities above 25 g/L with acquisition times ranging from 14 to 3 minutes which decline as cell density increases. This system has been employed to characterize the changes in intracellular state of a stationary phase culture which is subjected to a transition from aerobic to anaerobic conditions. Both intracellular NTP level and cytoplasmic pH are substantially lower under anaerobic conditions. Also, the system has been employed to observe the response of a growing culture to external addition of acetate. Cells are able to maintain pH difference across the cytoplasmic membrane at extracellular acetate concentrations of 5 and 10 g/L. However, acetate concentrations of 20 g/L cause collapse of the transmembrane ΔpH and sharp reduction of the growth rate of the culture. The experimental configuration described should also permit NMR observations of many other types of microbial cultures and of other nuclei. © 1993 John Wiley & Sons, Inc.
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    Plasmid burden in chemostat culture of Escherichia coli: Its effect on the selection for overproducers of host enzymes (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 41 (1993), S. 325-329 
    Details
    ISSN: 0006-3592
    Keywords: chemostat ; enzyme overproduction ; plasmid stability ; Escherichia coli ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The effect of plasmid-mediated metabolic burden of on the expression of the host genes and its consequences on the plasmid maintenance were studied in carbon-limited chemostat culture of Escherichia coli 1EA(pBR322) subject to selection for strains overproducing chromosomally coded ribitol dehydrogenase. The chemostat population became rapidly heterogeneous and the competition among evolved strains was found to be crucial for the kinetics of the plasmid loss from the culture. The selective disadvantages in growth rate associated with plasmid carriage in the parent-like and ribitol dehydrogenase-overproducing strains was estimated. © 1993 John Wiley & Sons, Inc.
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    Recombinant trypsin production in high cell density fed-batch cultures in Escherichia coli (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 41 (1993), S. 781-790 
    Details
    ISSN: 0006-3592
    Keywords: Escherichia coli ; recombinant ; fed batch ; high cell density ; trypsin ; fermention ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Fed-batch techniques were employed to obtain high cell density cultures (92-100 g DCW/L) of Escherichia coli strain X90 producing a recombinant serine protease, rat anionic trypsin, secreted to the periplasm. The specific growth rate was controlled to minimize growth-inhibiting acetate formation by utilizing an exponential feeding profile determined from mass balance equation. The volumetric yield of recombinant rat anionic trypsin was 56 mg/L, and the final cell density was 92 g DCW/L when the culture was induced in the late logarithmic phase. However, when the culture was induced in the early logarithmic phase, the volumetric yield was 13 mg/L and the final cell density was 14 g DCW/L. Thus, the induction timing is shown to have a significant effect on the final cell density as well as the overall volumetric yield of the recombinant protease. © 1993 Wiley & Sons, Inc.
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    Use of a simple mathematical model to predict the behavior of Escherichia coli overproducing β-lactamase within continuous single- and two-stage reactor systems (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 42 (1993), S. 557-570 
    Details
    ISSN: 0006-3592
    Keywords: mathematical model of cell growth ; continuous culture ; protein excretion ; β-lactamase ; Escherichia coli ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A simple mathematical model is developed to help explain the complex population dynamics of an Escherichia coli host-plasmid expression/excretion system for β-lactamase within single- and two-stage reactors. The model successfully integrates the individual regulatory (tac promoter induction), genetic (runaway plasmid replication), and population dynamics (culture instability) aspects of the system. The model predicts, and experiment confirms, that high-level β-lactamase production and excretion cannot be easily maintained in single-stage reactors using the current plasmid construction. Stable target protein production and excretion is mathematically predicted, and experimentally confirmed, within two-stage reactors. The model is used to provide insight into engineering a more stable host-vector expression/excretion system for use in single-stage reactors. © 1993 John Wiley & Sons, Inc.
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    Real-Time compensation of the inner filter effect in high-density bioluminescent cultures (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 42 (1993), S. 1190-1198 
    Details
    ISSN: 0006-3592
    Keywords: fermentation ; bioprocess monitoring ; bioluminescence ; inner filter effect ; Escherichia coli ; cell concentration monitoring ; fiber optic ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Bioluminescence has recently become a popular research tool in several fields, including medicine, pharmacology, biochemistry, bioprocessing, and environmental engineering. Beginning with purely qualitative goals, scientists are now targeting more demanding applications where accurate, quantitative interpretation of bioluminescence is necessary. Using the recent advances in fiber-optic technology, bioluminescence is easily monitored in vivo and in real time. However, the convenience of this measurement is often concealing an unsuspected problem: the bioluminescence signal might be corrupted by a large error caused by the extinction of light by biological cells. Since bioluminescent cultures not only emit light but also absorb and scatter it, the measured signal is related in a complex, nonlinear, and cell-concentration-dependent manner to the “true” bioluminescence. This light extinction effect, known as the “inner filter effect,” is significant in high-density cultures. Adequate interpretation of the bioluminescence signal can be difficult without its correction. Here, we propose a real-time algorithm for elimination of the inner filter effect in a bioreactor. The algorithm yields the bioluminescence which would be measured if the glowing culture was completely transparent. This technique has been successfully applied to batch and continuous cultivation of recombinant bioluminescent Escherichia coli. © 1993 John Wiley & Sons, Inc.
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    Nutrient-split feeding strategy for dialysis cultivation of Escherichia coli (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 41 (1993), S. 1092-1100 
    Details
    ISSN: 0006-3592
    Keywords: high cell density cultivation ; Escherichia coli ; XAD adsorbents ; dialysis reactor ; controlled substrate feed ; inhibitory products, removal of ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Reduction in nutrient loss during dialysis cultivation of Escherichia coli on a glycerol medium was investigated. A dialysis reactor with an inner fermentation and an outer dialysis chamber was used. Aerobic condition was maintained by limiting the glycerol feed rate to an optimum value which was estimated from the oxygen requirements for glycerol oxidation and oxygen transfer capacity of the reactor. High reduction in nutrient loss was achieved by using water as the dialyzing fluid. However, osmotic movement of water from the dialysis to the fermentation chamber was observed, and the final cell concentration was low. With a nutrient-split feeding strategy (feeding glycerol directly to the fermentation chamber and dialyzing with salt solution), glycerol loss was small, there was no osmotic flux of water to the fermentation chamber, and the cell concentration was high. Both glycerol and salt loss could be avoided, and a cell concentration of 170 g/L was obtained when the dialysis process was substituted by addition of XAD adsorbents to the dialysis chamber. Application of this nutrient-split feeding strategy to cell cultivation in a stirred tank reactor, coupled with dialysis in external dialyzer modules, resulted in low cell concentrations. © 1993 Wiley & Sons, Inc.
    Additional Material: 8 Ill.
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    URL: http://dx.doi.org/10.1002/bit.260411112
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  • 89
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    Plasmid retention and gene expression in suspended and biofilm cultures of recombinant Escherichia coli DH5α(pMJR1750) (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 41 (1993), S. 211-220 
    Details
    ISSN: 0006-3592
    Keywords: plasmid retention ; gene expression ; biofilm ; β-galactosidase ; segregational instability ; Escherichia coli ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Differences in plasmid retention and expression are studied in both suspended and biofilm cultures of Escherichia coli DH5α(PMJR1750). An alternative mathematical model is proposed which allows the determination of plasmid loss probability in both suspended batch and continuously fed biofilm cultures. In our experiments, the average probability of plasmid loss of E. coli DH5α(pMJR1750) is 0.0022 in batch culture in the absence of antibiotic selection pressure and inducer. Under the induction of 0.17 MM IPTG, the maximum growth rate of plasmid-bearing cells in suspended batch culture dropped from 0.45 h-1 to 0.35 h-1 and the β-galactosidase concentration reached an experimental maximum of 0.32. pg/cell 4 hours after the initiation of induction. At both 0.34 and 0.51 mM IPTG, growth rates in batch cultures decreased to 0.16 h-1, about 36% of that without IPTG, and the β-galactosidase concentration reached an experimental maximum of 0.47 pg/cell 3 hours after induction.In biofilm cultures, both plasmid-bearing and plasmid-free cells in increase with time reaching a plateau after 96 hours n the absence of both the inducer and any antibiotic selection pressure. Average probability of plasmid loss for biofilm-bound E. coli DH5β(pMJR1750) population was 0.017 without antibiotic selection. Once the inducer IPTG was added, the concentration of plasmid-bearing cells in biofilm dropped dramatically while plasmid-free cell numbers maintained unaffected. The β-galactosidase concentration reached a maximum in all biofilm experiments 24 hours after induction; they were 0.08, 0.1, and 0.12 pg/cel under 0.17, 0.34, and 0.51 mM IPTG, respectively. © 1993 John Wiley & Sons, Inc.
    Additional Material: 9 Ill.
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    URL: http://dx.doi.org/10.1002/bit.260410207
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  • 90
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    Improved penicillin amidase production using a genetically engineered mutant of Escherichia coli ATCC 11105 (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 41 (1993), S. 14-24 
    Details
    ISSN: 0006-3592
    Keywords: penicillin G amidase ; Escherichia coli ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Penicillin G amidase (PGA) is a key enzyme for the industrial production of penicillin G derivatives used in therapeutics. Escherichia coli ATCC 11105 is the more commonly used strain for PGA production. To improve enzyme yield, we constructed various recombinant E. coli HB101 and ATCC 11105 strains. For each strain, PGA production was determined for various concentrations of glucose and phenylacetic and (PAA) in the medium. The E. coli strain, G271, was identified as the best performer (800 U NIPAB/L). This strain was obtained as follows: an E. coli ATCC 11105 mutant (E. coli G133) was first selected based on a low negative effect of glucose on PGA production. This mutant was then transformed with a pBR322 derivative containing the PGA gene. Various experiments were made to try to understand the reason for the high productivity of E. coli G271. The host strain, E. coli G133, was found to be mutated in one (or more) gene(s) whose product(s) act(s) in trans on the PGA gene expression. Its growth is not inhibited by high glucose concentration in the medium. Interestingly, whereas glucose still exerts some negative effect on the PGA production by E. coli G133, PGA production by its transformant (E. coli G271) is stimulated by glucose. The reason for this stimulation is discussed. Transformation of E. coli G133 with a pBR322 derivative containing the Hindlll fragment of the PGA gene, showed that the performance of E. coli G271 depends both upon the host strain properties and the plasmid structure. Study of the production by the less efficient E. coli HB101 derivatives brought some light on the mechanism of regulation of the PGA gene. © 1993 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
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    URL: http://dx.doi.org/10.1002/bit.260410104
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  • 91
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    Enhancement of recombinant protein synthesis and stability via coordinated amino acid addition (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 41 (1993), S. 557-565 
    Details
    ISSN: 0006-3592
    Keywords: amino acid addition ; protein stability ; stress response ; Escherichia coli ; chloramphenicol-acetyl-transferase ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In this work, effective feeding schemes that would minimize stress responses to cloned-protein overexpression are investigated. The cloned-protein (chloramphenicolacetyl-transferase, CAT) contains a high aromatic amino acid content, most notably a high phenylalanine content. Experiments performed on Escherichia coli RR1 [pBR329] (constitutive promoter) and E. coli JM105 [pSH101] (inducible promoter) demonstrated that phenylalanine addition increases the rate of synthesis and yield of CAT. A previous study correlating inducer strength with CAT expression in E. coli JM105 [pSH101] indicated that the highest expression rate was accompanied by the highest apparent rate of protein degradation. In this work, the combined addition of isopropyl-β-D-thiogalactopyranoside (IPTG) and phenylalanine at intermediate levels resulted in substantial increase of CAT synthesis and partial reduction of protein degradation. Furthermore, transmission electron micrographs verified the absence of inclusion bodies, which, along with proteases, were suspected to reduce protein activity. The research demonstrates that significant enhancement in production and stability of heterologous proteins is possible by designing feeding strategies that incorporate knowledge of the interaction between primary cellular metabolism and foreign protein expression. © 1993 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/bit.260410508
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  • 92
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    Acute lung injury during bacterial or fungal sepsis (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Microscopy Research and Technique 26 (1993), S. 444-456 
    Details
    ISSN: 1059-910X
    Keywords: Escherichia coli ; Candida albicans ; Staphylococcus aureus ; Bacteremia ; Candidemia ; Cytokines ; TNF ; Adult respiratory distress syndrome ; Pulmonary edema ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: We compared physiological and ultrastructural indices of acute lung injury (ALI) during septic shock caused by taxonomically diverse pathogens to distinguish ALI due to endogenous inflammatory mediators vs. microbial exotoxins or other factors. Conscious rats were infected i.v. with gram-negativeEscherichia coli(EC, serotype 055:B5), exotoxin-C producing gram-positiveStaphylococcus aureus (SA), or yeast-phaseCandida albicans(CA, a clinical isolate). Viable inocula of 1010 EC, 1010 SA, or 109 CA caused lethal shock in 〈24 h, but distinct types of ALI were noted after bacteria vs. fungi. Within 0.5 h of EC infection, leukocytes marginated in the lung vasculature; by death at 6-14 h, animals were hyperoxemic but not acidemic, and showed slight interstitial edema with increased wet/dry weight ratios (W/D = 5.22 ± 0.10, mean ± SE, vs. 4.86 ± 0.07 in controls, P 〈0.05). Similarly mild ALI occurred after 1010 SA. In contrast, within 0.5 h of CA infection, yeast were visible within lung intravascular leukocytes. By death at 6-12 h, CA animals showed hyperoxic acidemia and moderate ALI with capillary obstruction, interstitial hemorrhage, and elevated lung W/D (5.52 ± 0.13, P 〈0.05 vs. controls) associated with yeast-mycelial transformation. Prior neutropenia accelerated mortality and worsened ALI after CA, with hypoxemic acidemia, increased lung W/D (7.23 ± 0.34, P 〈0.05 vs. other groups), capillary occlusion, perivascular and alveolar hemorrhage, and septal disruption by mycelia. Bacteremia induced large increases in serum tumor necrosis factor-α (TNF) and interleukin-1α within 1.5 h, but these cytokines remained low in CA animals, even at death. Neither survival nor ALI after EC or CA was altered by pentoxifylline, which attentuated TNF production, or by cyclooxygenase inhibition with ibuprofen. Thus, overall ALI severity correlated with physiological indices of pulmonary function, but ultrastructural changes correlated better with pathogen type than circulating cytokine or eicosanoid mediators. Whereas lethal bacteremia induced early cytokinemia and mild ALI with or without bacterial exotoxins, moderate ALI apparently was mediated by fungal exotoxins during lethal candidemia, which worsened during neutropenia due to enhanced mycelial proliferation.© 1993 Wiley-Liss, Inc.
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    URL: http://dx.doi.org/10.1002/jemt.1070260512
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  • 93
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    GTP hydrolysis in protein synthesis: two for Tu? (1993)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1993-02-26
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Schimmel, P -- New York, N.Y. -- Science. 1993 Feb 26;259(5099):1264-5.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Biology, Massachusetts Institute of Technology, Cambridge 02139.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/8446896" target="_blank"〉PubMed〈/a〉
    Keywords: Energy Metabolism ; Escherichia coli ; Guanosine Triphosphate/*metabolism ; In Vitro Techniques ; *Peptide Chain Elongation, Translational ; Peptide Elongation Factor Tu/*metabolism ; Ribosomes/*metabolism
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 94
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    Toward a model for the interaction between elongation factor Tu and the ribosome (1993)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1993-02-26
    Description: In the elongation cycle of bacterial protein synthesis the interaction between elongation factor-Tu (EF-Tu).guanosine triphosphate (GTP), aminoacyl-transfer RNA (aa-tRNA), and messenger RNA-programmed ribosomes is associated with the hydrolysis of GTP. This interaction determines the selection of the proper aa-tRNA for incorporation into the polypeptide. In the canonical scheme, one molecule of GTP is hydrolyzed in the EF-Tu-dependent binding of aa-tRNA to the ribosome, and a second molecule is hydrolyzed in the elongation factor-G (EF-G)-mediated translocation of the polypeptide from the ribosomal A site to the P site. Substitution of Asp138 with Asn in EF-Tu changed the substrate specificity from GTP to xanthosine triphosphate and demonstrated that the EF-Tu-mediated reactions involved the hydrolysis of two nucleotide triphosphates for each Phe incorporated. This stoichiometry of two is associated with the binding of the correct aa-tRNA to the ribosome.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Weijland, A -- Parmeggiani, A -- New York, N.Y. -- Science. 1993 Feb 26;259(5099):1311-4.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉SDI n. 61840 du Centre National de la Recherche Scientifique, Laboratoire de Biochimie, Ecole Polytechnique, Palaiseau, France.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/8446899" target="_blank"〉PubMed〈/a〉
    Keywords: Bacterial Proteins/metabolism ; Base Sequence ; Escherichia coli ; GTP Phosphohydrolase-Linked Elongation Factors/metabolism ; GTP-Binding Proteins/metabolism ; Guanosine Triphosphate/*metabolism ; Models, Biological ; Molecular Sequence Data ; *Peptide Chain Elongation, Translational ; Peptide Elongation Factor Tu/*metabolism ; RNA, Transfer, Amino Acyl/metabolism ; Ribosomes/*metabolism
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 95
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    A covalent enzyme-substrate intermediate with saccharide distortion in a mutant T4 lysozyme (1993)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1993-12-24
    Description: The glycosyl-enzyme intermediate in lysozyme action has long been considered to be an oxocarbonium ion, although precedent from other glycosidases and theoretical considerations suggest it should be a covalent enzyme-substrate adduct. The mutation of threonine 26 to glutamic acid in the active site cleft of phage T4 lysozyme (T4L) produced an enzyme that cleaved the cell wall of Escherichia coli but left the product covalently bound to the enzyme. The crystalline complex was nonisomorphous with wild-type T4L, and analysis of its structure showed a covalent linkage between the product and the newly introduced glutamic acid 26. The covalently linked sugar ring was substantially distorted, suggesting that distortion of the substrate toward the transition state is important for catalysis, as originally proposed by Phillips. It is also postulated that the adduct formed by the mutant is an intermediate, consistent with a double displacement mechanism of action in which the glycosidic linkage is cleaved with retention of configuration as originally proposed by Koshland. The peptide part of the cell wall fragment displays extensive hydrogen-bonding interactions with the carboxyl-terminal domain of the enzyme, consistent with previous studies of mutations in T4L.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Kuroki, R -- Weaver, L H -- Matthews, B W -- GM21967/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 1993 Dec 24;262(5142):2030-3.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Institute of Molecular Biology, Howard Hughes Medical Institute, University of Oregon, Eugene 97403.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/8266098" target="_blank"〉PubMed〈/a〉
    Keywords: Amino Acid Sequence ; Animals ; Bacteriophage T4/*enzymology ; Binding Sites ; Carbohydrate Conformation ; Carbohydrate Sequence ; Cell Wall/*metabolism ; Chickens ; Disaccharides/*metabolism ; Egg White ; Escherichia coli ; Molecular Sequence Data ; Muramidase/*metabolism ; Mutation ; Oligopeptides/*metabolism ; Peptidoglycan
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 96
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    Identification of the ferrioxamine B receptor, FoxB, inEscherichia coli K12 (1992)
    Springer
    BioMetals 5 (1992), S. 37-46 
    Details
    ISSN: 1572-8773
    Keywords: Escherichia coli ; ferrioxamine receptor ; iron transport ; photoaffinity label ; siderophores
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The photoreactivep-azidobenzoyl analog of ferrioxamine B was used to show that ferrioxamine-B-mediated iron transport is separate and distinct from coprogen-mediated iron transport inEscherichia coli. Photolysis of this analog inhibited uptake of [59Fe]ferrioxamine B but not [59Fe]coprogen or [59Fe]ferrichrome. Conversely, photolysis of thep-azidobenzoyl analog of coprogen B inhibited uptake of [59Fe]coprogen but not [59Fe]ferrioxamine B or [59Fe]ferrichrome. Photolabeling of outer membranes withp-azidobenzoyl-[59Fe]ferrioxamine B resulted in the labeling of two iron-regulated peptides with molecular masses of about 66 and 26 kDa. Expression of these peptides was increased when ferrioxamine B was the sole iron source. Both peptides were present in outer membrane preparations of thefhuF mutant H1717, but the 66 kDa peptide was not inducible. These results are evidence for an outer membrane receptor inE. coli unique for linear ferrioxamines.
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  • 97
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    DNA integration into recipient yeast chromosomes by trans-kingdom conjugation between Escherichia coli and Saccharomyces cerevisiae (1992)
    Springer
    Current genetics 21 (1992), S. 101-108 
    Details
    ISSN: 1432-0983
    Keywords: Trans-kingdom conjugation ; DNA integration ; Saccharomyces cerevisiae ; Escherichia coli
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary IncQ-derived conjugative shuttle vectors, which carried the yeast gene URA3 and/or the yeast autonomously replicating sequence (ARS1), were constructed. Both the ars-plus plasmid pAY205 and the ars-less plasmid pAY201 were successfully transmitted from E. coli to S. cerevisiae by the action of mob and tra. In this trans-kingdom conjugation, plasmid pAY205 could replicate and be retained in transconjugants. Plasmid pAY201 caused the formation of “micro-colonies” of abortive transconjugants due to its transient expression and rapid disappearance. Nevertheless, one per about 103 colonies caused by transmitted pAY201 plasmids were uncurable by integration into the homologous region of a yeast chromosome. Analyses by restriction enzyme mapping and Southern hybridization indicate that this integration is primarily caused by a double crossover during conjugation and not by a single reciprocal recombination.
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    URL: http://dx.doi.org/10.1007/BF00318467
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  • 98
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    An Escherichia coli mutant containing only demethylmenaquinone, but no menaquinone: effects on fumarate, dimethylsulfoxide, trimethylamine N-oxide and nitrate respiration (1992)
    Springer
    Archives of microbiology 158 (1992), S. 68-73 
    Details
    ISSN: 1432-072X
    Keywords: Demethylmenaquinone ; Menaquinone ; Anacrobic respiration ; Fumarate respiration ; Nitrate respiration ; Escherichia coli
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The mutant strain AN70 (ubiE) of Escherichia coli which is known to lack ubiquinone (Young IG et al. 1971), was analyzed for menaquinone (MK) and demethylmenaquinone (DMK) contents. In contrast to the wild-type, strain AN70 contained only DMK, but no MK. The mutant strain was able to grow with fumarate, trimethylamine N-oxide (TMAO) and dimethylsulfoxide (DMSO), but not with nitrate as electron acceptor. The membranes catalyzed anaerobic respiration with fumarate and TMAO at 69 and 74% of wild-type rates. DMSO respiration was reduced to 38% of wild-type activities and nitrate respiration was missing (≦8% of wild-type), although the respective enzymes were present in wild-type rates. The results complement earlier findings which demonstrated a role for DMK only in TMAO respiration (Wissenbach et al. 1990). It is concluded, that DMK (in addition to MK) can serve as a redox mediator in fumarate, TMAO and to some extent in DMSO respiration, but not in nitrate respiration. In strain AN70 (ubiE) the lack of ubiquinone (Q) is due to a defect in a specific methylation step of Q biosynthesis. Synthesis of MK from DMK appears to depend on the same gene (ubiE).
    Type of Medium: Electronic Resource
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  • 99
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    Iron control of the Vibrio fischeri luminescence system in Escherichia coli (1992)
    Springer
    Archives of microbiology 157 (1992), S. 235-241 
    Details
    ISSN: 1432-072X
    Keywords: Vibrio fischeri ; Luminescence ; Iron ; Escherichia coli ; Autoinduction ; lux Genes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Iron influences liminescence in Vibrio fischeri; cultures iron-restricted for growth rate induce luminescence at a lower optical density (OD) than faster growing, iron-replete cultures. An iron restriction effect analogous to that in V. fischeri (slower growth, induction of luminescence at a lower OD) was established using Escherichia coli tonB and tonB + strains transformed with recombinant plasmids containing the V. fischeri lux genes (luxR luxICD ABEG) and grown in the presence and absence of the iron chelator ethylenediamine-di (o-hydroxylphenyl acetic acid) (EDDHA). This permitted the mechanism of iron control of luminescence to be examined. A fur mutant and its parent strain containing the intact lux genes exhibited no difference in the OD at induction of luminescence. Therefore, an iron-binding repressor protein apparently is not involved in iron control of luminescence. Furthermore, in the tonB and in tonB + strains containing lux plasmids with Mu dI(lacZ) fusions in luxR, levels of β-galactosidase activity (expression from the luxR promoter) and luciferase activity (expression from the luxICDABEG promoter) both increased by a similar amount (8–9 fold each for tonB, 2–3 fold each for tonB +) in the presence of EDDHA. Similar results were obtained with the luxR gene present on a complementing plasmid. The previously identified regulatory factors that control the lux system (autoinducer-LuxR protein, cyclic AMP-cAMP receptor protein) differentially control expression from the luxR and luxICDABEG promoters, increasing expression from one while decreasing expression from the other. Consequently, these results suggest that the effect of iron on the V. fischeri luminescence system is indirect.
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    URL: http://dx.doi.org/10.1007/BF00245156
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  • 100
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    Dynamics of PhiX174 protein E-mediated lysis of Escherichia coli (1992)
    Springer
    Archives of microbiology 157 (1992), S. 381-388 
    Details
    ISSN: 1432-072X
    Keywords: PhiX174 ; Bacterial lysis ; Escherichia coli ; Electron microscopy ; Membranes ; Cell envelope
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Expression of cloned gene E of bacteriophage PhiX174 induces lysis by formation of a transmembrane tunnel structure in the cell envelope of Escherichia coli. Ultrastructural studies of the location of the lysis tunnel indicate that it is preferentially located at the septum or at polar regions of the cell. Furthermore, the diameter and shape of individual tunnel structures vary greatly indicating that its structure is not rigid. Apparently, the contours of individual lysis tunnels are determined by enlarged meshes in the peptidoglycan net and the force produced at its orifice, by the outflow of cytoplasmic content. Once the tunnel is formed the driving force for the lysis process is the osmotic pressure difference between cytoplasm and medium. During the lysis process areas of the cytoplasmic membrane which are not tightly attached to the envelope are extended inward by the negative pressure produced during lysis. After cell lysis external medium can diffuse through the lysis tunnel filling the inner cell space of the still rigid bacterial ghosts.
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    URL: http://dx.doi.org/10.1007/BF00248685
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