- Volume 120, Issue 2, 1980
Volume 120, Issue 2, 1980
- Physiology And Growth
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Studies on the Induction and Turnover of Citrate-oxidizing Capacity in Klebsiella aerogenes Using Chemostat Culture
More LessSteady-state chemostat cultures of Klebsiella aerogenes growing on a carbon-limited medium were challenged with pulses of carbon sources, and the resultant changes in dissolved oxygen tension were shown to reflect changes in respiration rate. These changes were used to study the kinetics of induction of citrate-oxidizing capacity, which is most probably limited by citrate permease, and the return to the preinduced state. Previously unexposed cells showed a lag phase, the duration of which decreased with increasing growth rate, with a minimum of 10min, followed by an induction phase of linear increase of citrate oxidation rate which continued as long as citrate was present. The rate of increase in activity, which can be equated to the rate of induction of citrate permease, was independent of citrate concentration but increased with growth rate. Previously exposed cells showed no lag and some residual activity before further induction. The kinetics of return to the preinduced state were unusual in that activity was short-lived with a half-life of 16 to 23 min while the lag took over 8 h to re-establish. The rate of decay of activity decreased with increasing growth rate.
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- Short Communication
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Comparison of the Antibacterial Activity of the Hypothiocyanite Anion towards Streptococcus lactis and Escherichia coli
More LessIt has been suggested that the antibacterial activity of the lactoperoxidase/thiocyanate/hydrogen peroxide system is due to the hypothiocyanite anion. Relatively pure solutions of hypothiocyanite can be prepared using an immobilized enzyme. These preparations have been used to examine the effect of the anion on the growth and on the membranes of Escherichia coli and Streptococcus lactis. Escherichia coli is killed in the presence ofthe anion whereas the effect on Streptococcus lactis is only bacteriostatic. As similar effects have been noted with the lactoperoxidase/thiocyanate/hydrogen peroxide system thehypothesis that the action of the two systems is similar is supported.
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Anaerobic Growth and Denitrification by Rhizobium japonicum and Other Rhizobia
More LessThe product of nitrate respiration in Rhizobium japonicum and a number of other rhizobia capable of anaerobic growth utilizing nitrate was N2O. No N2 or ammonia was formed. Nitrate reduction was linked to ATP formation during anaerobic but not during aerobic growth. Free-living rhizobia may remove fixed nitrogen from the soil by denitrification.
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Some Properties of Aspartate and Alanine Aminotransferases from Trichoderma viride
More LessAspartate aminotransferase (EC 2.6.1.1) and alanine aminotransferase (EC 2.6.1.2) were extracted from mycelia of Tricchoderma viride, partially purified and characterized. The pH optima for the enzyme activities were 9·0 and 8·6, respectively. Both enzymes were relatively stable at 37 °C but rapidly denatured at 60 °C. They were inducible by both l-aspartate and dl-alanine, but aspartate was the better inducer. The apparent Michaelis constants for aspartate aminotransferase when l-aspartate and 2-oxoglutarate were used were 7·14 mm and 1·32 mm, respectively. In the case of alanine aminotransferase, using dl-alanine and 2-oxoglutarate the corresponding values were 8·33 mm and 1·85 mm, respectively. The enzymes were competitively inhibited by succinate with K i values of 21 mm and 17 mm for aspartate aminotransferase and alanine aminotransferase, respectively. Both enzymes could use l-methionine whereas only aspartate aminotransferase could use l-tyrosine as amino donor.
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Occurrence of Cytochrome P-450 in Yeasts
More LessCytochrome P-450 was measured in whole cell suspensions of various yeasts, with Saccharomyces cerevisiae and S. uvarum (formerly carlsbergensis) serving as positive control species. Eleven yeasts, when grown on a medium with glucose (50 g 1−1) as carbon and energy source, contained cytochrome P-450. These were the Ascomycotina Debaryomyces hansenii, Hansenula anomala, Kluyveromyces fragilis, Pichia fermentans, Saccharomyces bayanus, S. chevalieri, S. italicus and Schizosaccharomyces japonicus, and the Deutero-mycotina Brettanomyces anomalus, Torulopsis dattila and T. glabrata. The amount of cytochrome P-450 varied 60- to 70-fold between the species. The position of the Soret band in reduced CO spectra also differed from one species to another. Cytochrome P-450 could not be detected in either Candida utilis or a Rhodotorula sp.
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Correlation of Glutamine Synthetase Activity with Cell Magnesium Concentration during Cell Division in Yeast Synchronized by Induction
More LessSynchronization of cell division in the fission yeast Schizosaccharomyces pombe and the budding yeast Kluyveromyces fragilis was achieved by induction using the DNA synthesis inhibitor 2′-deoxyadenosine and by a magnesium-exhaustion technique. The activity of glutamine synthetase in these synchronized cultures oscillated. Variations in the intracellular magnesium concentration were also observed, and peaks in magnesium concentration correlated with peaks in enzyme activity. We suggest that the enzyme from yeast is unstable and that its activity is regulated in vivo by changes in the intracellular concentration of magnesium.
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Characterization of Bacillus subtilis Mutants Temperature-sensitive in the Synthesis of Ribonucleic Acid
G. Mazza and P. PlevaniTwo mutants of Bacillus subtilis temperature-sensitive in RNA synthesis were isolated. One mutation (rna-20) was demonstrated to be an allele of a previously identified gene ( Riva et al., 1976 ). The other mutation (rna-16) identified a different gene and was mapped near aroI. The rna-16 mutation at the permissive temperature affected the spore outgrowth process. Purified RNA polymerase from rna-16 did not show any temperature sensitivity or structural defect.
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Excretion of Glutathione by Methylglyoxal-resistant Escherichia coli
More LessA methylglyoxal-resistant mutant of Escherichia coli B excreted glutathione into the growth medium, especially during growth on medium containing methylglyoxal. In the presence of methylglyoxal, the total amount of glutathione excreted was increased about 50-fold over that of the wild-type strain. The resistant mutant had high activities of two enzyme systems: a glutathione-forming enzyme system (consisting of γ-glutamylcysteine synthetase and glutathione synthetase) and a glyoxalase system (consisting of glyoxalase I and glyoxalase II). Methylglyoxal resistance appeared to be due to the simultaneous increase in the activities of these two enzyme systems.
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A Mutant of Aspergillus nidulans with a Reduced Level of Phenylalanine-binding Protein
More LessPartial purification of the phenylalanine-binding protein from Aspergillus nidulans mycelia, using Triton X-100 extraction and affinity chromatography on l-phenylalanine-CH-Sepharose, indicated that the p-fluorophenylalanine-resistant mutant, fpaD11, has a significantly reduced level of phenylalanine-binding protein compared with the wild type. This seems to be the cause of the reduced uptake of phenylalanine and consequent p-fluorophenylalanine-resistance of this mutant.
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- Taxonomy
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A Study of the Va-1 Group of Pseudomonads and its Relationship to Pseudomonas pickettii
More LessThe Va-1 group of denitrifying pseudomonads was characterized and compared with Pseudomonas pickettii (Va-2). They share many features but differ in their production of acid from cellobiose, lactose and maltose and in their denitrification (gas from nitrate) at 35 °C. DNA-DNA hybridizations between a strain of Va-1 and the type strain of P. pickettii disclosed 84% homology and hence indicated that Va-1 is a biovar of this species. Since both are potential human pathogens, features are presented that distinguish these and other phenotypically similar species that are recovered from clinical specimens.
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Evolution in Pseudomonas fluorescens
The relationships among 93 strains of Pseudomonas fluorescens were investigated by (1) a numerical taxonomic analysis on the results of 150 phenotypic tests, (2) DNA hybridization studies using 16 reference strains, (3) quantitative microcomplement fixation studies using six reference strains with antibodies directed against the protein azurin. In general, the strains fell into distinct clusters. Assignment to these clusters on the basis of azurin immunological similarity showed 98% agreement with assignment based on DNA homology, suggesting that many genes will follow the same pattern. Of the strains that clustered on the basis of genotype (DNA, azurin) 88% also clustered on the basis of phenotype. The occasional non-congruency observed between the genotypic and phenotypic data may be due to the variable rates of phenotypic evolution. These results provide a perspective on the roles of horizontal and vertical transfer of genes in the evolution of this bacterial group.
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