- Volume 101, Issue 2, 1977
Volume 101, Issue 2, 1977
- Biochemistry
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Free and Cellulose-bound Cellulases in a Cellulomonas Species
More LessA cellulolytic bacterium, identified as belonging to the genus Cellulomonas, produced two classes of cellulases when grown in the presence of cellulose. One class comprised enzymes which were tightly bound to cellulose, and the other, enzymes which were found free in the culture supernatant fluid. The cellulose-bound activity reached a maximum at the beginning of the stationary phase and then decreased, whereas the soluble activity increased to a plateau late in the stationary phase. The production of both classes of enzyme was repressed by adding cellobiose or glycerol to the cellulose. Deprivation of carbon sources did not induce cellulolytic activity. Cellobiose and sophorose showed only weak inducing activity in the absence of cellulose.
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Sterol Metabolism during Germination of Conidia of Aspergillus fumigatus
More LessThe sterol content of germinating conidia of the opportunistic pathogenic fungus Aspergillus fumigatus has been correlated with germination phase and sensitivity to polyene antibiotics. The sterol and sterol ester contents of walls did not change during germination. The sterol ester content of membranes and cell sap remained constant during germination, whereas the sterol content increased during the outgrowth of germ tubes. On the basis of differential extraction studies it was concluded that the loss of resistance to polyenes that occurred in the early stages of swelling of conidia during germination was not due to a movement of sterol or sterol ester out of the wall.
Radioactive-labelling experiments demonstrated that, although the amounts of conidial wall sterol and sterol ester did not change during germination, they were metabolically active. Changes in the turnover rate of wall and membrane sterol and sterol ester during germination were investigated and their relationship to a possible mechanism for the change from resistance to sensitivity to polyene antibiotics is discussed.
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Threonine Catabolism in Trypanosoma brucei
More Lessl-Threonine is catabolized by Trypanosoma brucei to give equimolar quantities of glycine and acetate. The pathway, which involves the two enzymes l-threonine dehydrogenase (EC 1.1.1.103) and aminoacetone synthase (acetyl-CoA: glycine C-acetyltransferase, EC 2.3.1.29) and subsequent hydrolysis of the acetyl-CoA, is most active in cultured trypanosomes but is also present in bloodstream forms. l-Threonine dehydrogenase from both culture and bloodstream forms of trypanosomes has an apparent molecular weight of between 28000 and 38000, and is sensitive to a wide range of sulphydryl reagents.
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Hydroxypyruvate Reductase Activity in Paracoccus denitrificans
More LessExtracts of Paracoccus denitrificans contain NADP-linked hydroxypyruvate reductase activity. The enzyme responsible has been separated and partially purified. It showed some activity with glyoxylate, acetoin, diacetyl and oxaloacetate and was 2 1/2 times as active with NADP as with NAD. It appears to be a constitutive enzyme and possible metabolic roles for it are discussed. Attention is drawn to the dangers of relying solely on the presence of hydroxypyruvate reductase as a diagnostic marker for the operation of a serine pathway of C1-assimilation in a micro-organism. The malate dehydrogenase from Pa. denitrificans has been partially purified and shown to possess no glycerate dehydrogenase or hydroxypyruvate reductase activity.
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Influence of Aerobic and Phototrophic Growth Conditions on the Distribution of Glucose and Fructose Carbon into the Entner-Doudoroff and Embden-Meyerhof Pathways in Rhodopseudomonas sphaeroides
More LessIn aerobically and phototrophically growing cells of Rhodopseudomonas sphaeroides, glucose and fructose catabolism were studied by means of enzyme analysis, radiorespirometry and incorporation of specifically-labelled glucose and fructose into spheroidene fractions, into alanine and into valine. Bacteria grown on glucose or fructose possessed all the enzymes necessary for sugar catabolism via the Entner-Doudoroff pathway. Bacteria grown on fructose also contained an inducible 1-phosphofructokinase, indicating that fructose was degraded via fructose 1-phosphate. Fructose was catabolized via both the Embden-Meyerhof and Entner-Doudoroff pathways. The contribution of each pathway to fructose breakdown was influenced by the growth conditions: under phototrophic conditions fructose was catabolized predominantly via the Embden-Meyerhof pathway; under aerobic conditions it was catabolized mainly via the Entner-Doudoroff pathway. This change in the major fructose catabolic pathway was paralleled by fructose-1, 6-bisphosphate aldolase activity: the activity was high in phototrophically growing cells and low in aerobically growing cells. Glucose, on the other hand, was catabolized via the Entner-Doudoroff pathway under both phototrophic and aerobic conditions.
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Evidence of Early Protein Synthesis Essential to the Spore Germination of Colletotrichum lagenarium
More LessThe biochemical events of spore germination of Colletotrichum lagenarium were investigated. Cycloheximide (3.55 m) inhibited spore germination when added during the first 40 min of incubation, but was ineffective when added after 40 min. Spores germinated when cycloheximide was removed from the suspension for 2 h during incubation, regardless of the length of pretreatment with cycloheximide. By pulse-labelling with [14C] glycine, it was evident that the protein which was synthesized during the first 40 min of incubation was indispensable for the initiation of germination, but protein synthesis which occurred at a later stage of incubation was not necessary for spore germination directly.
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Enzyme Regulation in Methylobacterium organophilum
More LessSeveral enzymes have been assayed in Methylobacterium organophilum grown on different substrates. The enzymes which are involved in growth on C1 compounds were induced by methanol and not repressed by succinate. When succinate-grown bacteria were resuspended in medium containing methanol, four enzymes unique to growth on C1 compounds (hydroxypyruvate reductase, serine-glyoxylate aminotransferase, methanol dehydrogenase and glycerate kinase) were fully induced by the time growth began. When methanol-grown bacteria were resuspended in medium containing succinate, all four enzyme activities decreased. Several mutants unable to grow on C1 compounds were examined for deficiencies in the enzymes specific for growth on these compounds. Seven of the mutants were pleiotropic, and six were not revertible by chemical mutagens, suggesting the possibility of genetic linkage or the presence of a regulon for the genes involved in C1 metabolism.
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- Development And Structure
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Determination of the Mass of Mycobacterium leprae by Electron Microscopy
More LessThe mass of Mycobacterium leprae, obtained as a pure suspension from tissues of infected armadillos, was measured electron microscopically using a technique that avoids the need for standards of mass. The mean mass of an individual bacterium was 3·9 ±1·0 (s.d.) ×10−14 g. Comparative measurements were also made on a small sample of M. lepraemurium (whose mass is known). Calculation of the mass of an individual bacterium allows numbers of bacteria in samples to be estimated by direct weighing rather than by counting.
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Effect of Tween 80 on the Morphology of Trigonopsis variabilis
More LessWhen Tween 80 (polyoxyethylene sorbitan mono-oleate) was given as a supplement in basal ammonium sulphate/glucose medium to the yeast Trigonopsis variabilis, it induced the development, throughout growth, of populations consisting almost entirely of triangular cells. This induction was inhibited by an increase in growth temperature and by adding specific concentrations of short-chain alcohols to the medium. Only Tween 80 among the Tween detergents and Span 80 (sorbitan mono-oleate) among the Span detergents induced the formation of triangular cells, and Brij 96 (polyoxyethylene-10-oleyl ether) and sodium oleate were ineffective. These results indicate that the ester-linked sorbitan oleate is the chemical characteristic which is responsible for the effect of Tween on the morphology of T. variabilis, in a system more reproducible than any other previously investigated.
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- Genetics And Molecular Biology
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Meiotic Gene Segregation in Rhizopus stolonifer
More LessResults obtained from the germination of mature zygospores of Rhizopus stolonifer support the hypothesis that normal meiotic processes operate in the sexual cycle of this fungus. The mating-type allele and a second allele, sul, segregated independently. When immature zygospores were germinated no such regularity was observed, but recombinant auxotrophic genotypes were recovered indicating a predormancy meiosis. However, prototrophic recombinants were not found. Bisexual heterokaryotic strains were also recovered from immature zygospore germinations but were auxotrophic. When cultures were obtained from outgrowths of both suspensors of a single zygospore the genotypes were not always those of the respective parents. This suggests the occurrence of nuclear movement from the immature zygospore to the suspensor cells.
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Morphological Stages of Bacillus subtilis Sporulation and Resistance to Fusidic Acid
More LessDuring spore development of Bacillus subtilis both protein synthesis and sporulation become resistant to the antibiotic fusidic acid. This resistance develops at the time when asymmetric prespore septa are formed. Simultaneously ribosomes lose their ability to bind fusidic acid, as demonstrated by their affinity chromatography with the immobilized drug. Mutants resistant to fusidic acid during growth are oligosporogenous; their sporulation development is blocked before septum formation. These results indicate that normal ribosomes are needed for prespore septation sporulation; only after septation can protein synthesis be maintained, throughout the development period, by fusidate resistant ribosomes.
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A Salmonella typhimurium Endonuclease that Converts Native DNA to Fragments of about 8 × 105 daltons
More LessCrude extracts of Salmonella typhimurium were found to contain an endonuclease that degraded double-stranded linear DNA from bacteria and phages to fragments with a molecular weight of about 8 x 105. The nuclease did not have an absolute requirement for Mg2+. One discrete intermediate product had a molecular weight of 6·6 × 106. Extracts from two different mutants were tested: one completely lacked the endonuclease activity (strain db5575), and the other showed an absolute requirement for Mg2+ (strain 4543). No biological role has yet been found for this endonuclease of S. typhimurium.
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- Medical Microbiology
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Studies on the Mechanism of Action of Oxygen-labile Haemolysins
More LessThe sensitivities of the binding step and the lytic step of haemolysis by pneumolysin to the action of various inhibitors and to variations in the assay conditions were studied. Binding was inhibited by HgCl2 and N-ethylmaleimide. Lysis by previously fixed lysin was insensitive to HgCl2 and only slightly sensitive to N-ethylmaleimide. Binding of pneumolysin was independent of ionic strength. Binding of pneumolysin and streptolysin O decreased above pH 8·0 and 8·4, respectively. These results suggest that binding requires a non-ionized unsubstituted sulphydryl group. Incubation of erythrocytes with NaF caused inhibition of pneumolysin, indicating that some metabolic function of the cell may be involved in lysis. The action of streptolysin O was not affected by NaF.
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- Physiology And Growth
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On the Induction of Zoosporogenesis in the Rumen Phycomycetes Neocallimastix frontalis, Piromonas communis and Sphaeromonas communis
More LessThe plant components inducing zoosporogenesis in the rumen phycomycetes Neocallimastix frontalis, Sphaeromonas communis and Piromonas communis were widely distributed in the plant kingdom with no apparent taxonomic relationship. In Lolium perenne L. (perennial rye-grass) and Hordeum distichon (barley), the components were principally present in the leaves and aerial tissues. Sufficient inducer was present in the normal diet of the host animal to trigger the differentiation and release of the zoospores from all the sporangia of each phycomycete species present in the rumen fluid tested. The inducers were unstable to oxygen, especially at elevated temperatures, and were destroyed by rumen micro-organisms. They may be similar compounds for each species.
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Interactions in a Methane-utilizing Mixed Bacterial Culture in a Chemostat
More LessThe interactions between the component species of a mixed bacterial culture grown on methane were investigated. The culture contained the methane-utilizing bacterium Methylococcus sp. and four heterotrophic bacteria which were unable to grow on methane but utilized products released by lysis of the Methylococcus sp. Products of methane oxidation such as methanol, formaldehyde and formate did not constitute a significant amount of the organic carbon found in the culture supernatant of the pure methane-utilizing bacterium grown in chemostat culture. The organic carbon was accounted for mainly as protein and nucleic acid and originated from a growth-dependent lysis of the methane-utilizing bacterium. In the mixed culture the level of the organic carbon was reduced and it is suggested that extracellular enzymes produced by the heterotrophic bacteria play a role in the degradation and utilization of these compounds. The major heterotrophic bacterium Pseudomonas sp. ncib11310 produced an extracellular neutral protease that degraded the proteins present in the culture supernatant of the methane-utilizing bacterium.
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Inactivation of Bacillus Spores in Dry Systems at Low and High Temperatures
More LessA plot of the thermal resistance of Bacillus subtilis var. niger spores (log D value) against temperature was linear between 37 and 190 °C (z = 23 °C), provided that the relative humidity of the spore environment was kept below a certain critical level. The corresponding plot for Bacillus stearothermophilus spores was linear in the range 150 to 180 °C (z = 29 °C) but departed from linearity at lower temperatures (decreasing z value). However, the z value of 29 °C was decreased to 23 °C if spores were dried before heat treatment. The straight line corresponding to this new z value was consistent with the inactivation rate at a lower temperature (60 °C). The data indicate that bacterial spores which are treated in dry heat at an environmental relative humidity near zero are inactivated mainly by a drying process. By extrapolation of the thermal resistance plot obtained under these conditions for B. subtilis var. niger spores, the D value at 0 °C would be about 4 years.
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The Cultivation of the Rumen Ciliate Entodinium bursa in the Presence of Entodinium caudatum
More LessThe rumen ciliate protozoon Entodinium bursa has been grown in vitro in the presence of bacteria and Entodinium caudatum for over a year at population densities of 100 to 200 ml−1. The medium contained potassium phosphate, prepared fresh rumen fluid, cysteine, wholemeal flour (or rice starch), dried grass and a culture of the spineless form of Entodinium caudatum. Entodinium bursa has an obligate requirement for this protozoon and died within 48 h in its absence. During growth from a 2% inoculum, the mean generation time of E. bursa was 6 h. Entodinium bursa engulfed 1·5 to 2·5 E. caudatum organisms h−1, and when E. caudatum was in excess it developed caudal spines for the first time in 17 years; these spined forms were engulfed much less readily than the spineless organisms.
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Effect of Amino Acids on Coremium Development in Penicillium claviforme
More LessAmino acids added to the growth medium stimulated development of coremium primordia in mycelium of Penicillium claviforme. Casein hydrolysate, l-asparagine, l-serine, l-glutamine, l-proline, l-hydroxyproline, l-glutamate and glycine accelerated development and also increased the final number of primordia per unit area of mycelium. A nearly linear relationship existed between the logarithm of casein hydrolysate concentration and the numbers of primordia developed, and a similar relationship was also shown with glutamate as nitrogen source. Mycelium developing from spores sown on agar plates showed some sites for coremium development within a few hours of germination, although most sites were not established until about 24 h later when the germlings had fused to form a network. At least 27 h exposure was required for amino acids to stimulate primordium development in 24 h-old mycelium. Cycloheximide, glucosamine and nystatin promoted primordium development at concentrations inhibiting hyphal growth; 2-deoxyglucose inhibited primordium formation. It was concluded that possible sites for coremia develop into primordia as a result of changes in nitrogen metabolism, and that local variations in the concentrations of certain amino acids or their metabolites may decide the pattern in which primordia form in the colony.
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Heterocyst Development in Anabaena cylindrica: The Necessity for Light as an Initial Trigger and Sequential Stages of Commitment
S. Bradley and N. G. CarrAn initial light-dependent stage in heterocyst formation in Anabaena cylindrica was observed. The length of the period of illumination, between 3 and 9 h, determined the frequency 0 mature heterocyst production. Sequential stages of commitment to both proheterocyst and heterocyst formation were shown by manipulation of the light period, ammonia, drugs and analogues. The modulated response of potential heterocyst-forming cells in a filament, requiring sustained periods of light and lack of nitrogen source, is described.
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The Apparent Influence of Atmospheric Oxygen Concentration on Nitrogenase Activity and Slime Production in Klebsiella pneumoniae Grown on a Solid Medium
More LessKlebsiella pneumoniae strains k11 and m5a1 which differ greatly in their ability to produce slime had similar ratios of nitrogenase activity when grown on agar under atmospheres of nitrogen, air or oxygen. With both strains, the rate of acetylene reduction was not significantly different when measured under air compared to nitrogen but was decreased under oxygen, which also restricted growth. Strain k11, the more slimy of the two strains produced more slime, as measured viscometrically, when the atmosphere above the agar contained a greater proportion of oxygen up to 50% O2. Strain m5a1 gave no detectable response to increased oxygen concentration other than decreased growth and nitrogenase activity under high oxygen concentration. Despite the superficial correlation between enhanced slime production and resistance to the potentially damaging effects of oxygen on nitrogenase in air-grown nitrogen-fixing Klebsiella, slime probably contributes only marginally to that resistance.
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- Short Communications
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