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  • 1
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Carbapenems are β-lactam antibiotics which have an increasing utility in chemotherapy, particularly for nosocomial, multidrug-resistant infections. Strain GS101 of the bacterial phytopathogen, Erwinia carotovora, makes the simple β-lactam antibiotic, 1-carbapen-2-em-3-carboxylic acid. We have mapped and sequenced the Erwinia genes encoding carbapenem production and have cloned these genes into Escherichia coli where we have reconstituted, for the first time, functional expression of the β-lactam in a heterologous host. The carbapenem synthesis gene products are unrelated to enzymes involved in the synthesis of the so-called sulphur-containing β-lactams, namely penicillins, cephamycins and cephalosporins. However, two of the carbapenem biosynthesis genes, carA and carC, encode proteins which show significant homology with proteins encoded by the Streptomycesclavuligerus gene cluster responsible for the production of the β-lactamase inhibitor, clavulanic acid. These homologies, and some similarities in genetic organization between the clusters, suggest an evolutionary relatedness between some of the genes encoding production of the antibiotic and the β-lactamase inhibitor. Our observations are consistent with the evolution of a second major biosynthetic route to the production of β-lactam-ring-containing antibiotics.
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 16 (1995), S. 0 
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: In recent years it has become clear that the production of N-acyl homoserine lactones (N-AHLs) is widespread in Gram-negative bacteria. These molecules act as diffusible chemical communication signals (bacterial pheromones) which regulate diverse physiological processes including bioluminescence, antibiotic production, piasmid conjugal transfer and synthesis of exoenzyme virulence factors in plant and animal pathogens. The paradigm for N-AHL production is in the bioluminescence (lux) phenotype of Photobacterium fischeri (formerly classified as Vibrio fischeri) where the signalling molecule N-(3-oxohexanoyl)-L-homoserine lactone (OHHL) is synthesized by the action of the Luxl protein. OHHL is thought to bind to the LuxR protein, allowing it to act as a positive transcriptional activator in an autoinduction process that physiologically couples cell density (and growth phase) to the expression of the bioluminescence genes. Based on the growing information on Luxl and LuxR homologues in other N-AHL-producing bacterial species such as Erwinia carotovora, Pseudomonas aeruginosa, Yersinia enterocolitica, Agrobacterium tumefaciens and Rhizobium legumino-sarum, it seems that analogues of the P. fischeri lux autoinducer sensing system are widely distributed in bacteria. The general physiological function of these simple chemical signalling systems appears to be the modulation of discrete and diverse metabolic processes in concert with cell density. In an evolutionary sense, the elaboration and action of these bacterial pheromones can be viewed as an example of multi-cellularity in prokaryotic populations.
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  • 3
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The enteric bacterium Serratia marcescens is an opportunistic human pathogen. The strain ATCC39006 makes the red pigment, prodigiosin (Pig), and the β-lactam antibiotic carbapenem (Car). Mutants were isolated that were concomitantly defective for Pig and Car production. These mutants were found to have a mutation in the rap gene (regulation of antibiotic and pigment). Sequence analysis of the rap gene revealed a predicted protein product showing strong homology to SlyA, originally thought to be a haemolytic virulence determinant in Salmonella typhimurium. Homologues of rap were detected in several bacterial genera, including Salmonella, Yersinia, Enterobacter, and species of the plant pathogen, Erwinia. The Erwinia horEr (homologue of rap) and the Yersinia horYe genes were also found to be very similar to rap and slyA. Marker exchange mutagenesis of horEr revealed that it encoded a regulatory protein controlling the production of antibiotic and exoenzyme virulence determinants in the phytopathogen, Erwinia carotovora subspecies carotovora. We have shown that these new homologues of SlyA form a highly conserved subgroup of a growing superfamily of bacterial regulatory proteins controlling diverse physiological processes in human, animal and plant pathogens.
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  • 4
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The pheromone N-(3-oxohexanoyl)-L-homoserine lactone (OHHL) regulates expression of bioluminescence in the marine bacterium Vibrio fischeri, the production of carbapenem antibiotic in Erwinia carotovora and exoenzymes in both E. carotovora and Pseudomonas aeruginosa. A characteristic feature of this regulatory mechanism in V. fischeri is that it is cell density-dependent, reflecting the need to accumulate sufficient pheromone to trigger the induction of gene expression. Using a lux plasmid-based bioluminescent sensor for OHHL, pheromone production by E. carotovora, Enterobacter agglomerans, Hafnia alvei, Rahnella aquatilis and Serratia marcescens has been demonstrated and shown also to be cell density-dependent. Production of OHHL implies the presence in these bacteria of a gene equivalent to luxl. Chromosomal banks from all five enteric bacteria have yielded clones capable of eliciting OHHL production when expressed in Escherichia coli. The luxl homologue from both E. carotovora (carl) and E. agglomerans (eagl) were characterized at the DNA sequence level and the deduced protein sequences have only 25% identity with the V. fischeri Luxl. Despite this, carl, eagl and luxl are shown to be biologically equivalent. An insertion mutant of eagl demonstrates that this gene is essential for OHHL production in E. agglomerans.
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  • 5
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: We have constructed a novel promoter probe plasmid pSB40, containing a unique lac-α-tetracycline marker gene tandem, which allows for both positive and negative selection of active promoters. Promoters cloned in pSB40 can be readily mobilized as EcoR1 cassettes. Using this vector we have performed a non-invasive analysis of the E. coli chromosome for promoters regulated by osmotic upshift. Only one such promoter, subsequently identified as part of the proU operon, was isolated. A sequence of 253bp, sufficient to mediate osmotic regulation of the proU promoter, was defined. This E coli promoter was normally regulated in Salmonella typhimurium, Klebsiella and Citrobacter but not in Shigella. A proU-luxAB fusion plasmid was constructed and used to monitor in vivo real-time kinetics of proU induction following osmotic upshock.
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  • 6
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The proU loci of Salmonella typhimurium and Escherichia coli encode high-affinity glycine betaine transport systems which play an important role in survival under osmotic stress. Transcription of the proU locus is tightly regulated by osmolarity and this regulation appears to be mediated by osmotically induced changes in DNA supercoiling. In order to study the regulatory mechanisms involved we have cloned and characterized the proU locus of S. typhimurium by an in vivo transductional procedure. The locus is shown to consist of at least three genes, designated proVWX, cotranscribed as a single operon. The first gene in the operon encodes a protein sharing considerable sequence identity with ATP-binding proteins from other periplasmic transport systems. Unexpectedly, the highly expressed periplasmic glycine betaine binding protein was found to be encoded by a distal gene, proX, in the operon. The operon has no significant internal promoters but is expressed from a single osmoregulated promoter whose transcription start site has been mapped. The proU promoter of E. coli has also been sequenced and the transcription start site shown to be similar to that of S. typhimurium. Evidence is presented which suggests that, besides de novo glycine betaine uptake, an important function of ProU may be the recapture and recycling of other osmolytes that leak from the cell.
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  • 7
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Members of two genera of Gram-negative bacteria, Serratia and Erwinia, produce a β-lactam antibiotic, 1-carbapen-2-em-3-carboxylic acid. We have reported previously the cloning and sequencing of the genes responsible for production of this carbapenem in Erwinia carotovora. These genes are organized as an operon, carA–H, and are controlled by a LuxR-type transcriptional activator, encoded by the linked carR gene. We report in this paper the genetic dissection of this putative operon to determine the function of each of the genes. We demonstrate by mutational analysis that the products of the first five genes of the operon are involved in the synthesis of the carbapenem molecule. Three of these, carABC, are absolutely required. In addition, we provide evidence for the existence of a novel carbapenem resistance mechanism, encoded by the carF and carG genes. Both products of these overlapping and potentially translationally coupled genes have functional, N-terminal signal peptides. Removal of these genes from the Erwinia chromosome results in a carbapenem-sensitive phenotype. We assume that these novel β-lactam resistance genes have evolved in concert with the biosynthetic genes to ensure ‘self-resistance’ in the Erwinia carbapenem producer.
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Journal of industrial microbiology and biotechnology 19 (1997), S. 286-293 
    ISSN: 1476-5535
    Keywords: Keywords: major cold-shock protein; PCR; universal primer oligomers; bacterial detection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The detection of bacteria using PCR is a well-established diagnostic technique. However, conventional PCR requires the use of DNA primer oligomers that are specific to the target organism and, as a consequence, a sample can only be tested for the presence of that specific target. A significant advantage would be to probe a sample for the presence of any bacteria, followed by identification. To achieve this it is necessary to identify a DNA sequence common to all bacteria. Here we demonstrate that such a sequence may be that encoding the major cold-shock proteins. Using two universal PCR primer oligomers from conserved regions of these gene homologues, we have amplified a 200 base-pair DNA sequence from more than 30 diverse Gram-positive and Gram-negative bacteria, including representatives from the genera Aeromonas, Bacillus, Citrobacter, Enterobacter, Enterococcus, Escherichia, Klebsiella, Lactobacillus, Lactococcus, Listeria, Pediococcus, Photobacterium, Proteus, Salmonella, Shigella, Staphylococcus, Streptococcus, and Yersinia. Sequence analysis of the amplified products confirmed a high level of DNA homology. Significantly, however, there are sufficient nucleotide variations to allow the unique allocation of each amplified sequence to its parental bacterium.
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  • 9
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Bioluminescence and Chemiluminescence 8 (1993), S. 267-291 
    ISSN: 0884-3996
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: The following references encompass a review of recent literature where the in vivo expression of eukaryotic and/or prokaryotic luciferases provide for sensitive reporters of cellular activity. The list is subdivided into prokaryotic and eukaryotic applications. We have included the uses of luciferases in elucidating the control of gene expression or for monitoring cell viability. We have not included papers cited by Stanley and Stewart (J Biolumin Chemilumin 1990; 5:141-52) nor have we included papers on the structure and regulation of luciferases as this now substantial literature will be the subject of a future review. References cited in both this review and previous ones are referred to by the number assigned to them in the earlier review.
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  • 10
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Bioluminescence and Chemiluminescence 5 (1990), S. 115-122 
    ISSN: 0884-3996
    Keywords: in vivo bioluminescence ; biocides ; virucides ; sub-lethal injury ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: The detection of specific bacterial pathogens, indicator microorganisms and antimicrobial substances, and the recovery of microorganisms from sub-lethal injury, are all aspects of importance to industry which are currently being targeted using in vivo bioluminescence. In all instances, a key requirement for the application of bioluminescence is the establishment of a strict correlation between in vivo bioluminescence and cell viability, as determined by colony counting on agar plates. Comparative studies for biocides (phenol, chlorhexidine diacetate, phenol thioether), for a virucide (hypochlorite) and for cellular recovery of S. typhimurium from sub-lethal injury, all indicate that such a correlation is valid. Furthermore, real-time measurements of in vivo bioluminescence reveal a major population of bacterial cells that retain functional intracellular biochemistry, but are defective in their ability to replicate post of freeze injury.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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