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  • Mutation  (2,975)
  • Cells, Cultured  (1,353)
  • American Association for the Advancement of Science (AAAS)  (4,093)
  • Springer  (123)
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  • 1
    Electronic Resource
    Electronic Resource
    Mechanisms of tetracycline and rifampicin resistance inBacteroides fragilis mutants obtained by ionizing radiation (1988)
    Springer
    Journal of industrial microbiology and biotechnology 3 (1988), S. 299-304 
    Details
    ISSN: 1476-5535
    Keywords: Anaerobe ; Antibiotic resistance ; Irradiation ; Mutation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Based on a dose-survival curve, a radiation dose of 3.99 C/kg was used to induce antibiotic-resistant mutants inBacteroides fragilis. Escherichia coli B/r membrane fragments were employed as a reducing agent. Antibiotic-resistant mutants ofB. fragilis were utilized to study the mechanism by which these organisms become resistant to selected chemotherapeutic agents. Decreased accumulation of tetracycline by resistant mutants ofB. fragilis suggests that the resistance to this antibiotic is associated with the outer membrane permeability. There is a marked difference in the inhibitory action of rifampicin on RNA polymerase activity in rifampicin-sensitive and-resistant strains ofB. fragilis. This enzyme is, therefore, the likely target for inhibition of bacterial growth in this anaerobe by rifampicin.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01569530
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  • 2
    Electronic Resource
    Electronic Resource
    Beijerinckia indica var.penicillanicum penicillin V acylase: enhanced enzyme production by catabolite repression-resistant mutant and effect of solvents on enzyme activity (1991)
    Springer
    Journal of industrial microbiology and biotechnology 7 (1991), S. 209-214 
    Details
    ISSN: 1476-5535
    Keywords: Penicillin V acylase ; Beijerinckia indica var.penicillanicum ; Mutation ; Solvent effect
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Beijerinckia indica var.penicillanicum mutant UREMS-5, producing 168% more penicillin V acylase, was obtained by successive treatment with UV, γ-irradiation and ethylmethane sulfonate. Penicillin V acylase production by the mutant strain was resistant to catabolite repression by glucose. Incorporation of glucose, sodium glutamate and vegetable oils in the medium enhanced enzyme production. The maximum specific production of penicillin V acylase was 244 IU/g dry weight of cells. Effect of solvents on hydrolysis of penicillin V by soluble penicillin V acylase and whole cells was studied. Methylene chloride, chloroform and carbon tetrachloride significantly stimulated the rate of penicillin V hydrolysis by whole cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01575885
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  • 3
    Electronic Resource
    Electronic Resource
    Use of continuous-flow UV-induced mutation technique to enhance chlorinated organic biodegradation (1991)
    Springer
    Journal of industrial microbiology and biotechnology 8 (1991), S. 99-106 
    Details
    ISSN: 1476-5535
    Keywords: Mutation ; UV ; Biodegradation ; Chlorinated organic compound
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary In this study, a continuous-flow UV-induced mutation (CUM) device and the CUM device coupled to a selector (CUMS) reactor were fabricated and tested for their ability to enhance the probability of obtaining populations capable of chlorinated organic biodegradation. A mixed culture of bacteria were used as the starting strain for both the CUM and CUMS processes. Populations were obtained from the CUM and CUMS systems capable of 4-chlorobenzoic acid, 2,4-dichlorobenzoic acid and chlorendic acid biodegradation. Non-UV irradiated population served as controls for the experiments and did not demonstrate chlorinated organic biodegradation over the test duration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01578760
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  • 4
    Electronic Resource
    Electronic Resource
    Growth ofZymomonas on lactose: Gene cloning in combination with mutagenesis (1989)
    Springer
    Journal of industrial microbiology and biotechnology 4 (1989), S. 19-27 
    Details
    ISSN: 1476-5535
    Keywords: Zymomonas mobilis ; Growth on lactose ; Cloning ; Mutation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Wild-type strains ofZymomonas mobilis have a limited substrate range of glucose, fructose and sucrose. In order to expand this substrate range, transconjugants ofZ. mobilis containing Lac+ plasmids have been constructed. Although β-galactosidase is expressed in such strains, they lack the ability to grow on lactose. We now report the development ofZ. mobilis strains capable of growth on lactose. This was achieved in two stages. First, a broad host range plasmid was constructed (pRUT102) which contained the lactose operon under the control of aZ. mobilis promoter plus genes for galactose utilization.Z. mobilis CP4.45 containing pRUT102 was then subjected to mutagenesis combined with continued selection pressure for growth on lactose. One strain,Z. mobilis SB6, produced a turbid culture that yielded 0.25% ethanol from 5% lactose (plus 2% yeast extract) in 15 days.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01569689
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  • 5
    Electronic Resource
    Electronic Resource
    Comparison of symbiotic effectiveness of Rhizobium sp. with positive hydrogen-uptake activity compared with negative mutants in relation to nitrogen fixation in mungbean (Vigna radiata L.) (1995)
    Springer
    Biology and fertility of soils 20 (1995), S. 270-274 
    Details
    ISSN: 1432-0789
    Keywords: Mungbean ; Vigna radiata ; Nitrogen fixation ; Hydrogen uptake ; Mutation ; Nitrosoguanidine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract H2 uptake activity was well distributed in Rhizobium sp. strains isolated from nodules of mung-bean (Vigna radiata L.). Two effective strains, RMP1 und RMP2, exhibiting significantly higher H2 uptake activity were subjected to mutagenesis with nitrosoguanidine. The respective mutation frequencies were 0.18 and 0.19%. Three Hup- mutants each of RMP1 und RMP2 were compared with the wild-type parent strains under pot culture experiments to evaluate the significance of the H2 uptake system in biological N2 fixation. Nodulation capabilities, plant growth characteristics, and the chlorophyll content of the leaves were significantly reduced in the plants treated with Hup- mutants. Nitrogenase activity in Hup- nodules was reduced by 8–41%. Similarly, N accumulation was also reduced singificantly.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00336089
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  • 6
    Electronic Resource
    Electronic Resource
    Mutational analysis of the upstream activation site of yeast ribosomal protein genes (1989)
    Springer
    Current genetics 15 (1989), S. 247-251 
    Details
    ISSN: 1432-0983
    Keywords: Yeast ; Ribosomal protein gene ; Transcription activation ; Mutation ; Methylation interference
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Most ribosomal protein (rp-)genes in yeast are preceded by conserved sequence motifs that act as upstream transcription-activating sites (RPG box). These sequence elements have previously been shown to represent specific binding sites for a protein factor, TUF. Comparison of the various nucleotide elements identified so far indicates a remarkably high degree of variation in the respective sequences. On the other hand, a methylation interference study performed with one RPG box revealed close contact points with the TUF protein along the entire sequence. To investigate the sequence requirements of the RPG box, we inserted synthetic oligonucleotides that differed from the general consensus sequence ACACCCATACATTT at single positions into a deletion mutant of the L25 promoter that lacked its natural RPG elements. Transcription activity was estimated by Northern analyses of the cellular level of L25-galK hybrid transcripts. The results show that in the 3′ part of this sequence element single substitutions are allowed at all positions, in the 5′ part, however, the nucleotide requirements appear to be more stringent. In particular, the invariant C at position 5 of the consensus sequence is absolutely necessary for its enhancer function.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00447039
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  • 7
    Electronic Resource
    Electronic Resource
    Generation of new functional mutant alleles by premeiotic disruption of the Neurospora crassa am gene (1990)
    Springer
    Current genetics 18 (1990), S. 441-445 
    Details
    ISSN: 1432-0983
    Keywords: Neurospora crassa ; Mutation ; RIP phenomenon
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary In the further analysis of a cross in which the mis-sense allele, am 3, of the Neurospora crassa am (glutamate dehydrogenase) gene was present in one parent together with two ectopic wild-type gene copies, one ascus was identified in which the two ectopic copies had been inactivated by the RIP process whereas the am 3 allele continued to produce its characteristic enzyme variety in active, but heat-sensitive, form. The am 3 allele had also acquired a new HindIII restriction site. It had no detectable methylation. The mutations responsible respectively for the new restriction site and the modified enzyme properties were separated from each other, and from the original am 3 mutation, by selecting for intragenic recombination on either side of the am 3 site. In this way two new effectively wild-type alleles were generated, one characterised by its heat-sensitive and kinetically modified enzyme product and the other by a new HindIII site. These results demonstrate that the RIP phenomenon can be a source of new functional alleles.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00309914
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  • 8
    Electronic Resource
    Electronic Resource
    The calcitonins: An example of unusual evolution (1972)
    Springer
    Journal of molecular evolution 1 (1972), S. 258-262 
    Details
    ISSN: 1432-1432
    Keywords: Calcitonin ; Evolution ; Genetic Code ; Mutation ; Amino Acid Sequences ; Base Changes ; Phylogeny
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The amino acid replacements in the calcitonins from five different species (human, bovine, ovine, porcine and salmon) have been analyzed according to the genetic code. More mutations separate the presumed common mammal from the artiodactyls than from either salmon or man.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01660245
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  • 9
    Electronic Resource
    Electronic Resource
    Codon usage in muscle genes and liver genes (1983)
    Springer
    Journal of molecular evolution 19 (1983), S. 214-218 
    Details
    ISSN: 1432-1432
    Keywords: Codon: anticodon adaptation ; Mutation ; Selection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Synonymous codon usage frequencies, derived from cDNA clone sequences, were compared for several sets of vertebrate genes. Gene sets as diverse as those expressed in avian skeletal muscle and in mammalian liver showed similar patterns of synonymous codon usage. There were no significant differences suggesting tissue-specific co-adaptation of codon usage patterns and tRNA anticodon profiles. The results indicate a consensus codon usage pattern for vertebrate genes which is largely independent of taxonomic class, tissue of expression, and the cellular fate and rate of evolution of the encoded proteins. Certain elements of the consensus codon usage pattern indicate that it is the product of natural selection and not simply a mutational equilibrium among phenotypically equivalent synonyms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02099968
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  • 10
    Electronic Resource
    Electronic Resource
    Selection againstdam methylation sites in the genomes of DNA of enterobacteriophages (1985)
    Springer
    Journal of molecular evolution 21 (1985), S. 317-322 
    Details
    ISSN: 1432-1432
    Keywords: dam Methylase ; 6-Methyladenine ; Daughter-strand repair ; Mutation ; Selection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Postreplicative methylation of adenine inEscherichia coli DNA to produce G6m ATC (where6mA is 6-methyladenine) has been associated with preferential daughter-strand repair and possibly regulation of replication. An analysis was undertaken to determine if these, or other, as yet unknown roles of GATC, have had an effect on the frequency of GATC inE. coli or bacteriophage DNA. It was first ascertained that the most accurate predictions of GATC frequency were based on the observed frequencies of GAT and ATC, which would be expected since these predictors take into account preferences in codon usage. The predicted frequencies were compared with observed GATC frequencies in all available bacterial and phage nucleotide sequences. The frequency of GATC was close to the predicted frequency in most genes ofE. coli and its RNA bacteriophages and in the genes of nonenteric bacteria and their bacteriophages. However, for DNA enterobacteriophages the observed frequency of DNA enterobacteriophages the observed frequency of GATC was generally significantly lower than predicted when assessed by the chi square test. No elevation in the rate of mutation of6mA in GATC relative to other bases was found when pairs of DNA sequences from closely related phages or pairs of homologous genes from enterobacteria were compared, nor was any preferred pathway for mutation of6mA evident in theE. coli DNA bacteriophages. This situation contrasts with that of 5-methylcytosine, which is hypermutable, with a preferred pathway to thymine. Thus, the low level of GATC in enterobacteriophages is probably due not to6mA hypermutability, but to selection against GATC in order to bypass a GATC-mediated host function.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02115649
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