- Volume 73, Issue 2, 1972
Volume 73, Issue 2, 1972
- Biochemistry
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Myo-inositol Catabolism in Salmonella typhimurium: Enzyme Repression Dependent on Growth History of Organism
More LessSUMMARY: Biochemical and genetic evidence suggests that NADPH-dependent 2-keto-myo-inositol reductase and 2-keto-myo-inositol dehydratase are associated with myo-inositol catabolism in Salmonella typhimurium. When growth of this organism is initiated in salts medium containing citrate and inositol using a citrate-grown inoculum, ketoinositol reductase is virtually completely repressed. By contrast, when inositol-grown organisms are used as inoculum, a relatively high level of the enzyme is present in bacteria even after a 20-fold increase in mass in the citrate + inositol medium. Under these conditions, inositol is used for growth to a significant extent, and citrate is utilized to a lesser extent than when growth is started with citrate-grown organisms. Thus by varying the growth history of the organism, different biochemical phenotypes can be produced without any change in the genotype or in the immediate environmental conditions.
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The Effects of Canavanine and of Arginine Starvation on Macromolecular Synthesis in Chlamydomonas reinhardi
More LessSUMMARY: Chlamydomonas reinhardi, starved of arginine, stopped growing but remained viable and continued to make protein. Synthesis of DNA and the accumulation of stable species of RNA were severely inhibited. Synthesis of rapidly labelled RNA was initially inhibited, but only temporarily, and finally rapidly labelled RNA was made faster than with arginine. These disturbances in nucleic acid metabolism were not related to changes in the pool sizes of nucleotide triphosphates, nor were any new nucleotides, such as guanosine tetraphosphate, detectable. When arginine in the medium was replaced by canavanine, the cells lost their chlorophyll, became non-motile, and non-viable. Canavanine rapidly inhibited the synthesis of RNA, but only inhibited the incorporation of amino acids into protein or the synthesis of DNA after a long lag. The size of the pools of nucleotide triphosphates and the pattern of their labelling with adenine was changed. These effects were consistent with a mechanism of killing, involving replacement of arginine by canavanine, by the cytoplasmic protein-synthesizing system. This protein then prevented all RNA synthesis. No changes in the structure of the nucleus were detected. Chlamydomonas reinhardi, therefore, differs from Escherichia coli in its response to arginine starvation or treatment with canavanine.
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Thymine and Uracil Catabolism in Escherichia coli
More LessSUMMARY: Growing Escherichia ccli wild-type and pyrimidine-deficient strains break down exogenously added pyrimidine bases, thymine and uracil, whose 2-carbon atom appears as CO2. By using mineral salts glucose media with different sources of nitrogen the degradation processes are shown to be inducible. We conclude that thymine and uracil catabolism are regulated by the amount of metabolically available nitrogen in the ce|l.
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Esterase Activity of Streptolysin-O
More LessSUMMARY: Purified streptolysin-O, from group-C streptococci, H46A, whose identity with NAD-glycohydrolase (EC.3.2.2.5) was reported earlier, has been shown to hydrolyse 4-nitrophenyl-esters. With 4-nitrophenylacetate as substrate, Km was 6.6 × 10~5 M; turnover number was 10000 mol substrate/mol enzyme/min and optimum pH was 7.8 to 8.5. Esterase activity was activated by SH-compounds and inhibited by diisopropylphosphofluoridate, mercuric salts and oxidizing agents. The effects of these agents on esterase activity were similar to their effects on the haemolytic activity of streptolysin-O protein so that both catalytic processes may be accomplished by the same active site.
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- Development And Structure
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Calcium Dipicolinate-provoked Germination and Outgrowth of Spores of Clostridium pasteurianum
More LessSUMMARY: Germination of heat-activated spores of Clostridium pasteurianum was rapidly induced by treatment with calcium dipicolinate; 90% of the spores lost their refractility within 20 min at 37°C. The sequence of ultrastructural changes during germination and subsequent outgrowth in a nutrient medium, was followed by electron microscopy. Dissolution of the spore cortex was accompanied by escape of cortical material via numerous perforations in the spore coat. The spore core underwent pre-emergent swelling to fill the space vacated by the cortical material, and eventual rupture of the spore coat led to emergence of the germling cell which invariably occurred via the open base of the exosporium. Thus, specimens of residual spore ‘husks’, prepared by the critical point drying procedure, consisted of intact exosporia enclosing surprisingly large fragments of the original spore coats.
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The Exosporium of Clostridium pasteurianum
More LessSUMMARY: Autolytically liberated spores of Clostridium pasteurianum possessed an open-ended exosporium, which scanning electron microscopy showed as a flimsy integument draped around the rigid spore body. Critical point drying prevented collapse of the exosporium and a material connexion between spore and exosporium was observed in specimens prepared by this technique. A variety of electron-microscopic techniques showed that the exosporium possessed a relatively simple multilamellar structure, each lamella consisting of subunits arranged in paracrystalline array which in surface view displayed hexagonal symmetry. Possible model structures based on these findings are considered.
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Flagellum Degeneration in the Fungus Phytophthora palmivora (formerly Phytophthora parasitica)
More LessSUMMARY: Direct sporangial germination in Phytophthora palmivora (formerly Phytophthora parasitica) is accompanied by a regular series of events leading to the complete breakdown of all flagella present in the mature sporangia. Electron microscopy of thin sections shows that the breakdown involves the cleavage of the ensheathing flagellar vacuoles into small vesicles, thus leaving the axonemes unenclosed in the cytoplasm. In a second stage the axonemal microtubules lose their parallel arrangement and gradually disintegrate. The central microtubules break down first and thus appear to be more fragile than the peripheral ones.
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Detection of Bacteriochlorophyll-containing Micro-organisms by Infrared Fluorescence Photomicrography
More LessSUMMARY: Fluorescence in the near infrared of individual photosynthetic bacteria was photographed through the microscope with infrared sensitive film. The fluorescence was also observed directly with an infrared sensitive image converter.
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- Genetics And Molecular Biology
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DNA Competition Studies within the Bacillus cereus Group of Bacilli
More LessSUMMARY: The relatedness between strains of bacilli in the Bacillus cereus group has been studied by DNA/DNA competition using the memberane filter technique. Strains of B. cereus, B. thuringiensis and of B. anthracis form a closely related group, in which B. thuringiensis can be distinguished from B. cereus. Bacillus megaterium includes a wider range of strains, some of which are closely related to B. cereus, B. thruringiensis and B. anthracis.
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Surface Changes in a Strain of Rhizobium trifolii on Mutation to Bacteriophage Resistance
More LessSUMMARY: A strain of Rhizobium trifolii and four phage-resistant derivatives had different mutation frequencies to phage resistance. One mutant adsorbed the phage to which it was resistant; the others showed little or no adsorption. Differences between the strains in the number and nature of ionizable surface groups were revealed by micro-electrophoresis. Two of the resistant mutants were lysed by lysozyme and three by lipase. Lysozyme + EDTA lysed all strains, but at different rates.
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Evolutionary Mechanism of Adaptation of Arthrobacter histidinolovorans and Pseudomonas aeruginosa to Use L-Histidinol as a Sole Source of Nitrogen and Carbon
More LessSUMMARY: Mechanisms whereby Arthrobacter histidinolovorans and Pseudomonas aeruginosa grow on L-histidinol as sole source of carbon and nitrogen have been examined.
Polyacrylamide gel electrophoresis (PAGE) showed two distinct histidinol dehydrogenase (HDH) bands in partially purified Arthrobacter histidinolovorans extracts: HDH(B) was always present but increased up to twofold by growth with histidine; HDH(I), additionally present only in histidinol-grown organisms, which had up to 10 times the total and specific HDH activity of organisms grown on salts+glucose medium. HDH biosynthesis was not repressed by histidine, glucose+ammonia or glutamate. HDH(I) could have evolved from HDH(B) by gene duplication and modification, with the resulting gene acquiring a new, inducible control mechanism.
A mutant, hnc-I, of Pseudomonas aeruginosa grew on histidinol as sole source of carbon and nitrogen, which the wild-type did only poorly. Only one HDH band was found on PAGE of partially purified extracts of either mutant or wild-type, however grown, though histidinol-grown hnc-I showed a more intense band and 60 times the HDH activity of glucose+salts-grown organisms. Histidine, glucose+ammonia or glutamate abolished this HDH increase. Here the adaptation seemed to consist of an additional control mechanism giving rise to high levels of the normal HDH when histidinol was sole source of carbon and nitrogen.
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Properties of Ribosomes from Acanthamoeba castellanii
J. H. Parish and L. HallSUMMARY: Polyribosomes were isolated from vegetative cells of Acanthamoeba castellanii NEFF. Ribosomes, of sedimentation coefficient 97 S, were isolated from vegetative cells and cysts. Both polyribosomes and ribosomes dissociated in 0.3 M-KC1 to particles of sedimentation coefficients 66, 53 and 40 S, and a slowly sedimenting particle whose sedimentation coefficient was not measured. RNA was extracted from the particles and fractionated. The 53 S and 40 S particles are the ribosomal subunits; the 97 and 66 S particles contained RNA characteristic of both subunits.
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Circular DNA Molecules Controlling Synthesis and Transfer of the Surface Antigen (K88) in Escherichia coli
More LessSUMMARY: Studies have been carried out on the molecular nature of the plasmid DNA in four strains of Escherichia coli carrying different mutants of the K88 factor. The factor was derepressed in three of the strains, one of which had kept the K88 antigen determinant, while the antigen was no longer demonstrable in the two other strains. The fourth strain possessed the K88 antigen but was transfer defective. The purified plasmid DNA was studied by electron microscopy and analytical CsCl density gradient centrifugation.
All the plasmid DNA from the four strains formed a single band in the neutral CsCl gradient at a density of 1.709 g/cm3. The distributions of the contour lengths of the circular DNA molecules indicate three principal size classes of about 5, 20 and 25 µm. The small, 5 µm circles presumably contain the K88 determinant. The results seem to support the theory of a dissociation of composite plasmids.
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Genetic Recombination in Caulobacter
More LessSUMMARY: Auxotrophic, phage-resistant and streptomycin-resistant mutants of Caulobacter were used to demonstrate genetic recombination in this genus. Forty of a possible 170 mating pairs gave recombinant frequencies of from 100 to 1000 times greater than reversion frequencies for the markers used. Stability of the recombinants was demonstrated by successive cloning on both complete and minimal medium. Cell contact is apparently required for recombination since both cell types of a mating pair must be present for prototroph formation.
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- Physiology And Growth
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A Chemostat Study of the Effect of Fixed Nitrogen Sources on Nitrogen Fixation, Membranes and Free Amino Acids in Azotobacter chroococcum
More LessSUMMARY: Increasing concentrations of ammonium ions in the medium of nitrogen-fixing, sulphate-limited continuous cultures of Azotobacter chroococcum caused a proportionate repression of nitrogenase activity; free NH4 + could be detected in the extracellular culture fluid only when nitrogenase activity was wholly repressed. The NH4 + concentrations giving 50% or 100% repression were proportional to the population density. Nitrate ions repressed with similar stoichiometry; glutamate, glutamine and aspartate did not repress and were not metabolized; repressed and derepressed populations contained equal amounts and proportions of glutamate-forming enzymes. Repressed populations lacked both enzymatic components of nitrogenase. The intracellular free amino acid pools were typical of Gram-negative bacteria; an increase in the degree of repression was associated with an increase in the pool levels of ammonia, aspartate and glutamate. Nitrogen-fixing populations possessed a convoluted intracytoplasmic membrane system which was absent from ammonia-assimilating organisms, but the phospholipid contents of the two types of population were similar. All members of a half-repressed population possessed these membranes, but to a lesser extent that fully derepressed populations.
When N2-fixing chemostat populations were abruptly exposed to repressive concentrations of ammonium succinate. repression occurred exponentially and nitrogenase activity disappeared from the culture faster than wash-out of stable enzyme. Repression was not alleviated by exogenous cyclic AMP. Derepression was complete, according to the acetylene test, within half a doubling time of disappearance of free ammonium ions from the culture.
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End-products, Fermentation Balances and Molar Growth Yields of Homofermentative Lactobacilli
More LessSUMMARY: Y(glucose) values for Lactobacillus plantarum, L. delbrueckii, L. casei, L. lactis and L. bulgaricus, grown as batch cultures in defined medium, and L. casei, grown in complex medium, were 20.0 to 33.3.Y(galactose) values for L. plantarum were 25.7 to 32.5. Each species produced acetate in addition to lactate, and Y(ATP) values, corrected for the energy produced simultaneously with the formation of acetate, were 10.0 to 10.9, close to 10.5, proposed as a standard value by Bauchop & Elsden (1960). Neither formate nor ethanol was produced in more than trace quantities. Y(glucose) values determined for L. lactis and L. bulgaricus at 40 °C were less than 50% of those determined at 37 °C. Production of lactate and acetate accounted for all of the glucose utilized at both temperatures, indicating that the production of ATP by L. lactis or L. bulgaricus at 40 °C was not coupled closely to the utilization of ATP in the synthesis of bacterial mass.
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Permeability of Phenyl-Hg+-resistant and Phenyl-Hg+-susceptible Isolates of Pyrenophora avenae to the Phenyl-Hg+ Ion
More LessSUMMARY: The permeability of two phenyl-Hg+-resistant and two phenyl-Hg+-susceptible isolates of Pyrenophora avenae Ito & Kuribay. to the phenyl-Hg+ ion was investigated. Similar amounts of phenyl-Hg+ entered the living mycelium of both resistant and susceptible isolates. No difference was detected in the numbers of thiol groups present on the wall, although the apparent free space of susceptible isolates toward the phenyl-Hg+ ion was greater than that of resistant isolates. The mechanism of resistance to the phenyl-Hg+ ion is probably based on a detoxification mechanism involving the binding of the toxic ion to metabolically inessential molecules within the mycelium.
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Competition among Amino Acids for Incorporation into Methylococcus capsulatus
More LessSUMMARY: Amino acid uptake by Methylococcus capsulatus was found to be effected by a transport system common to a wide range of amino acids. Some correlation existed between the amount of an amino acid incorporated and its effectiveness as a competitor against other amino acids, thus indicating different affinities among amino acids for the transport system. Uptake of some amino acids (e.g. the aromatic group and lysine) by an additional mechanism(s) is also suggested. Relief of threonine-inhibition of growth by metabolically related and unrelated amino acids is explained in terms of inhibition by other amino acids of the accumulation into the organisms of bacteriostatic levels of threonine. The threonine-resistant mutants isolated had decreased capacities to incorporate threonine and all the other amino acids tested.
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Effect of Tetrathionate on the Growth of a Marine Thiobacillus
More LessSUMMARY: Thiobacillus sp. strain IV-85, an isolate from the marine environment, oxidized thiosulphate in two sequential logarithmic phases. Tetrathionate accumulated in the partially spent broth during the first logarithmic phase, and reached a maximum concentration at the time of transition to the second logarithmic phase. Tetrathionate added during the early first logarithmic phase caused a decrease in the rate of thiosulphate utilization similar to that observed after the transition from the first to second logarithmic phase. Bacteria harvested from the first logarithmic phase resisted 0.1 mM-cyanide which inhibited oxygen uptake by bacteria harvested from the second logarithmic phase. Rhodanese (thiosulphate: cyanide sulphur transferase, EC. 2.8.1.1) was detected in extracts of bacteria from both phases. Tetrathionate accumulation in the growth medium inhibited rhodanese activity, resulting in the transition of thiosulphate utilization from the first to second logarithmic phase.
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Influence of Culture pH on the Content and Composition of Teichoic Acids in the Walls of Bacillus subtilis
More LessSUMMARY: Teichoic acids were invariably present in the walls of Bacillus subtilis var. niger and B. subtilis W23 grown in chemostats at D = 0.25 h−1, 35 °C, pH 7.0 in media containing non-limiting concentrations of phosphate, but they possessed little ester-bound alanine. However, varying the culture pH between 8.0 and 5.0 effected changes not only in the amount but also in the ester-bound alanine content of wall teichoic acids of both organisms. The walls of phosphate-limited B. subtilis var. niger were devoid of teichoic acid when grown at pH 7.0, but not at lower pH, when this polymer again contained ester-bound alanine. The magnesium binding properties of these wall preparations were also determined. The results showed that walls containing ester-bound alanine in the teichoic acid bound the same amount of magnesium as walls in which the teichoic acid was unsubstituted by alanine.
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- Short Communication
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The Polar Lipids of Some Species of Nocardia
More LessSUMMARY: Mannophosphoinositides appear to be widespread among the Actinomycetales. Besides the well-known mycobacterial source, they are also present in streptomyces, microbispora (Kataoka & Nojima, 1967; Tabaud, Tisnovska & Vilkas, 1971), nocardias (Yano, Furukawa & Kusunose, 1969) and corynebacteria (Brennan & Lehane, 1971) and a related phosphorus-free mannoinositide is prominent in propionibacteria (Prottey & Ballou, 1968; Shaw & Dinglinger, 1969). Prompted by the unusual observation of a monomannophosphoinositide in Corynebacterium aquaticum (Khuller & Brennan, 1972) we have examined in more detail three species of Nocardia, and find that mannophosphoinositides, which are always of the dimannosyl type, are barely evident in Nocardia polychromogenes, whereas in N. coeliaca, they are among the most obvious phospholipids. Glucose-containing phospholipids and glycolipids are always prominent.
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- Taxonomy
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Numerical Analysis of the Genera Saccharomyces and Kluyveromyces
More LessSUMMARY: Numerical analysis of the 41 species currently recognized in the genus Saccharomyces indicated that only 23 clusters were sufficiently different, at less than 90% matching of 58 characters, to be classified as separate species. These species belonged to four main divisions of the genus, mutually related at 70 to 75% matching: Saccharomyces cerevisiae group (twelve species), S. exiguusgroup (seven species), S. florentinus group (three species) and S. rouxii. By similar analysis of the genus Kluyveromyces, three groups were recognized; the first, of twelve species, was associated with Kluyveromyces lactis, which, related at 70% to the four groups of Saccharomyces, may be regarded as a fifth group of that genus. The second group of Kluyveromyces is a single species, K. veronae, which is related to the S. cerevisiae group. The third group of Kluyveromyces, five former species related to K. africanus, is closely related to S. exiguus. The genera Saccharomyces and Kluyveromyces overlap and it is proposed that they be regarded as a single genus, Saccharomyces. In the combined genus there are 34 species, assessed at 90% matching coefficient. A list of proposed synonyms is presented, with modified standard descriptions of those species in which the synonyms are merged.
The advantages of serological identification over a scheme based on fermentation and assimilation are discussed; yeast isolates may be allocated rapidly to one of the major taxonomic groups by agglutination and examination of morphology.
Saccharomyces rouxii characteristically reacted with serum A, and S. exiguus group usually with serum D, although occasionally also with sera A or B. The groups of species associated with Kluyveromyces lactis, S. cerevisiae and S. florentinus were antigenically heterogeneous, but were distinguished by morphology of the cells.
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Volumes and issues
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Volume 170 (2024)
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