- Volume 104, Issue 1, 1978
Volume 104, Issue 1, 1978
- Sgm Special Lecture
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- Biochemistry
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Cytochrome Formation, Oxygen-induced Proton Extrusion and Respiratory Activity in Streptococcus faecalis var. zymogenes Grown in the Presence of Haematin
More LessStreptococcus faecalis var. zyrnogenes was grown in oxygen-limited continuous culture in a lactate/tryptone/yeast extract medium containing 7·5μg haematin ml−l. Low temperature difference spectra of whole organisms and washed membranes showed two peaks in the cytochrome b region, at 558 nm and 562 nm, and a peak at 627 nm indicative of a d-type cytochrome. A CO-binding cytochrome was also present in the haematin-grown bacteria. These cytochromes were not detected in bacteria grown without haematin. The haematin- grown bacteria produced proton pulses in a weakly buffered medium when pulsed with oxygen-saturated buffer. The average →H+/O ratio of such pulses was 1·4 and they were abolished by carbonyl cyanide m-chlorophenylhydrazone (CCCP). The haematin-grown bacteria had a high activity of particulate NADH oxidase, at least 10 times that of bacteria grown without haematin. They also had a high lactate Q 02 which was strongly inhibited by CCCP and gramicidin whereas bacteria grown without haematin had a very low lactate Q 02 largely insensitive to the uncoupling agents. The glucose Q 02 was similar in bacteria grown in the presence or absence of haematin but was stimulated by uncoupling agents in haematin- grown organisms and slightly inhibited by these agents in organisms grown without haematin. These results confirm earlier findings of the ability of S. faecalis to form a functional cytochrome system in the cell membrane when supplied with haematin and show that electron transport to oxygen by such a system is coupled to proton translocation.
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Purification and Properties of β-Hydroxybutyrate Dehydrogenase from Mycobacterium phlei atcc354
More Lessβ-Hydroxybutyrate dehydrogenase (EC 1.1.1.30) was purified 145-fold from Mycobacterium phlei ATCC354 by ammonium sulphate fractionation and DEAE-cellulose chromatography. The pH optima for oxidation and reduction reactions were 8.4 and 6.8 respectively. The purified enzyme was specific for NAD, NADH, acetoacetate and d( − )-β-hydroxybutyrate. K m values for dl-β-hydroxybutyrate and NAD were 7·4 mm and 0.66 mM respectively. The enzyme was inactivated by mercurial thiol inhibitors and by heat, but could be protected by NADH, Ca2+ and partially by Mn2+. The enzyme did not require metal ions and was insensitive to EDTA, glutathione, dithiothreitol, β-mercaptoethanol and cysteine.
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- Ecology
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Soil Fungistasis: Role of Volatile Inhibitors in Two Soils
W. H. Ko and F. K. ChowVolatile inhibitors were detected in Conover loam and sandy loam soils by incubating spores on double layer cellophane over, but separated from, soil in a Petri dish. Spores of Exserohilum rostratum and Alternaria solani which were not inhibited by the volatile inhibitors did not germinate in soils. Three other inhibitor-sensitive fungi were not affected by the amount of volatile inhibitors emanated from 0·5 g of soils, but they failed to germinate when incubated in that amount of soil. Attempts to remove volatile inhibitors from soils by aeration did not increase spore germination. Results suggested that volatile inhibitors from these soils were of secondary importance and superimposed upon fungistasis caused mainly by nutrient deprivation.
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- Genetics And Molecular Biology
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Linkage Relationships Between Mutants of Methylobacterium organophilum Impaired in their Ability to Grow on One-carbon Compounds
More LessEight mutant strains of Methylobacterium organophilum which are capable of growing on succinate but not on methanol are described. Three of these contain single enzyme deficiencies while five have pleiotropic deficiencies. Some of the mutant strains are revertible to the wild-type phenotype by N-methyl-N′-nitro-N-nitrosoguanidine and ethyl methanesulphonate and others are not.
Crosses between strains were performed by transformation using DNA prepared from cells which were streptomycin-resistant and either methanol+ or methanol−. The frequencies of streptomycin-resistant transformants and methanol+ transformants were determined independently. Four of the methanol− mutant strains appeared to contain mutations which are linked to each other (group 1) while the other four (group 2) appeared to contain mutations not linked to the first four. In reciprocal crosses with the group 2 markers, two appeared to be linked to each other, while the other two were not linked to any mutant tested.
The data presented were used to construct a model for the organization of these genes in which the CO-binding cytochrome c is not linked to the five genes for C1-specific enzymes. In this model, the expression of six C1-specific functions is controlled by a common regulatory agent.
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- Medical Microbiology
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Virulence and Resistance to Superoxide, Low pH and Hydrogen Peroxide among Strains of Mycobacterium tuberculosis
More LessSix strains of Mycobacterium tuberculosis of different virulence in guinea-pigs were compared with regard to their resistance to low pH, to hydrogen peroxide (H2O2) at different pH values and to superoxide(·02−). Low virulence was associated with susceptibility to H2O2 in native and isoniazid-resistant strains but not in laboratory-attenuated strain h37ra. H2O2 resistance was only partly related to catalase content. Low virulence was not associated with susceptibility to an acid environment but the tuberculocidal effect of H2O2 was significantly increased at low pH. The strains were uniformly resistant to ·02− and contained similar amounts of superoxide dismutase. The implications of these observations are discussed in the context of mechanisms of host defence in tuberculosis.
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- Physiology And Growth
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Evidence for the Production of Ethylene by the Mycelium of Agaricus bisporus and its Relationship to Sporocarp Development
More LessThe increased production of ethylene that occurs during the development of sporocarps of Agaricus bisporus results from increased formation by the compost but not by the casing layer. The increase depends on the presence of sporocarps up to a critical point in their development. It is concluded that the mycelium of A. bisporus in the compost is responsible for this ethylene production because no significant bacterial flora was found in the compost from fruiting cultures, and the mycelium growing on complex agar media also liberated ethylene. Mycelium growing on defined synthetic medium also evolved ethylene if methionine was supplied.
From the results of the different assays, there was no evidence for a regulatory role of ethylene in growth or development of A. bisporus.
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The Effects of Temperature and Growth Rate on the Proportion of Unsaturated Fatty Acids in Bacterial Lipids
More LessThe effects of temperature and growth rate on the fatty acid composition of the extractable lipids of four mesophilic and three psychrotrophic bacteria were examined. Two of the mesophiles (Escherichia coli and Pseudomonas aeruginosa) increased the proportion of unsaturated fatty acids in their lipids with decreasing temperature over their whole growth temperature range. The other mesophiles (Enterobacter aerogenes and Lactobacillus casei) increased the proportion of unsaturated fatty acids with decreasing temperature only over the lower half of their growth temperature ranges. The psychrotrophs Pseudomonas fluorescens and Enterobacter sp. had a constant proportion of unsaturated acids over the lower half of their growth temperature range, while the psychrotrophic Lactobacillus sp. showed no consistent change in its unsaturated fatty acid composition with temperature. All species showed some variation of unsaturated fatty acid composition with growth rate at the highest and lowest growth temperatures, although such variations were small in some species (Ent. aerogenes and Lactobacillus sp.).
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Exopolysaccharide Production by Pseudomonas ncib11264 Grown in Continuous Culture
More LessExopolysaccharide formation by Pseudomonas ncibii264 in a single-stage continuous culture was maximal under nitrogen limitation with excess carbohydrate substrate at 30±1 °C and pH 7·0±0·1 Polysaccharide production was not enhanced by phosphate limitation but was dependent on the dilution rate. Steady states were maintained for up to 500 h without deterioration of the culture or the development of mutant strains. The efficiency of conversion of the glucose substrate utilized into exopolysaccharide by the chemostat cultures was as high as 73%.
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Pectic Enzymes of Pigmented Strains of Clostridium
More LessThe pectic enzymes of six strains of pigmented, pectolytic clostridia isolated from potatoes were examined and compared with those strains of Clostridium felsineum and Clostridium aurantibutyricum using cup-plate assays. The organisms could be divided into two groups. Group 1 consisted of the potato isolates and the strain of C. aurantibutyricum; these formed pectic lyase enzymes and pectinesterase but no pectic hydrolase. Group 2 consisted of eight strains of C. felsineum (and one culture labelled Clostridium roseum); these formed pectic lyase and pectic hydrolase but no detectable pectinesterase. Viscometric studies and analyses of degradation products of pectate formed by enzymes of four representative strains from group 1 and two strains from group 2 showed that all these clostridia formed endopectate lyase enzymes; studies of one enzyme preparation showed that the pH optimum was about 9·5. In addition, the group 2 organisms formed endopolygalacturonase and probably also exopolygalacturonase.
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Trypanosoma (Schizotrypanum) dionisii: Effect of Various Agents on Attachment and Entry to Macrophages in vitro and on Morphogenesis
More LessThe attachment and entry of Trypanosoma dionisii to mouse peritoneal macrophages in vitro were studied. Both occurred to a similar extent whether parasites were alive or heat-killed, and whether macrophages were obtained from normal or immunized mice. Attachment occurred equally at 4 and 37 C, but entry only occurred at the higher temperature. Neither was affected by pretreatment of parasites with active or inactivated complement. Entry, but not attachment, was inhibited by cytochalasin B; both were inhibited by trypsin. Immune mouse plasma (if inactivated) stimulated attachment but not entry (within 24 h). It also stimulated intracellular replication of T. dionisii by multiple fission and subsequent differentiation (probably within macrophages) to small extracellular trypomastigotes. No extracellular parasite and only scanty intracellular forms survived 120 h in cultures containing non-inactivated immune mouse plasma. It was concluded that attachment (in the absence of antibody) occurred to non-specific receptors in the macrophage membrane and was followed by phagocytosis of the parasites rather than their active penetration of the cell.
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The Prediction of Growth Yields in Methylotrophs
More LessEquations have been developed for assimilation of methane, methanol, methylamine, dimethylamine, trimethylamine, formaldehyde and formate into cell material by bacteria using the ribulose monophosphate pathway, the ribulose bisphosphate pathway and the serine pathway of carbon assimilation. The equations have been used for predicting the effect on cell yields (Y s, Y o2 and Y co2) of various P/O ratios, systems for substrate oxidation and assimilation pathways. The generalizations relating P/O ratios and cell yields, which have been used previously for such calculations, are not always applicable to methylotrophs. In particular, for the majority of methylotrophs the growth yield is determined by NAD(P)H supply as well as ATP supply, and for some methylotrophs growth yields may be exclusively NAD(P)H-limited. Because of this NAD(P)H limitation, the concept of Y ATP in methylotrophs should be used with extreme caution.
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Zoospore Chemotaxis in the Rumen Phycomycete Neocallimastix frontalis
More LessNeocallimastix frontalis zoospores showed chemotaxis to a range of carbohydrates, but not to the common amino acids, purines, pyrimidines or vitamins. Four chemoreceptors were identified: the glucose receptor, sensitive to d-glucose, d-galactose, d-xylose, l-sorbose, d-fucose and 2-deoxy-d-glucose; the sucrose receptor, sensitive to sucrose, d-fructose and raffinose; the mannose receptor, sensitive to d-mannose and d-glucose; and the sorbitol receptor, sensitive to d-sorbitol and d-mannitol. Growth of the vegetative stage of N. frontalis did not occur with d-xylose, l-sorbose, d-fucose, 2-deoxy-d-glucose, raffinose, d-mannose or d-sorbitol. The zoospores were attracted to carbohydrate mixtures representing the soluble carbohydrates found in different barley tissues; the highest response was with those mixtures representing carbohydrates of awn and inflorescence tissue. Chemotaxis also occurred preferentially to the awn and inflorescence tissue carbohydrate combinations rather than to carbohydrate combinations representing other tissues. Germination of the zoospores occurred in medium containing glucose in excess of 10−4 m.
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- Short Communications
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- Taxonomy
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Use of Canonical Variates Analysis in Differentiation of Bacteria by Pyrolysis Gas-Liquid Chromatography
More LessLow-resolution pyrolysis gas-liquid chromatography (p.g.l.c.) can differentiate genera of aerobic food spoilage bacteria. Multivariate statistical techniques were applied but neither principal components nor furthest neighbour cluster analysis produced a consistent differentiation although both confirmed the reproducibility of p.g.l.c. When the distance between genera was redefined in terms of Mahalanobis D 2 - a generalized concept taking into account scatter around the mean - good differentiation was observed and could be displayed graphically by plotting the genus group means relative to the first two canonical variate axes. The coefficients of the canonical variates provide a strategy for discriminating between the genus groups. Some practical problems in the identification of unknowns using this technique are discussed.
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Base Composition, Size and Sequence Similarities of Genome Deoxyribonucleic Acids from Clinical Isolates of Pseudomonas putrefaciens
More LessThe mean base compositions of DNA from 27 strains of Pseudomonas putrefaciens, P. rubescens and P. piscicida ranged from 43·4 to 53·2 mol % GC with genome sizes from 3·04 × 109 to 4·23 × 109 daltons. On the basis of in vitro DNA-DNA binding, estimated spectrophotometrically from initial renaturation rates, P. putrefaciens strains were heterogeneous in the extent to which they shared similar nucleotide sequences, and were divided into four DNA homology groups. The DNA characteristics of strains in these groups correlated with several biochemical characteristics that facilitated identification of clinical isolates of P. putrefaciens. The two species P. putrefaciens and P. rubescens appear to be synonymous and none of the four groups of P. putrefaciens was related in DNA sequences to P. piscicida. Pseudomonas putrefaciens should therefore be retained as a single species and characteristics for identifying the various groups within the species are listed.
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Numerical Taxonomy of Phylloplane Bacteria Isolated from Lolium perenne
More LessPhenetic data on over 600 heterotrophic bacteria from green leaves of Lolium perenne s24 were collected and analysed using numerical taxonomic methods. Marker strains representing 60 taxa were included in the analyses. At similarity levels of 80 % or above, 74 % of the isolates were recovered in six major and 45 minor phena. Four of the major phena were equated with the taxa Listeria grayi/murrayi, Pseudomonas fluorescens, Staphylococcus saprophyticus and Xanthomonas campestris; the two unidentified phena contained pink, Gram-negative rods with polar flagella. Xanthomonads and pink chromogens formed high populations in May, xanthomonads and pseudomonads in July, xanthomonads in September and listeriae and staphylococci in October. It seems that despite the spatial proximity of leaves, litter and soil, each of these habitats contains independent bacterial communities with specific properties.
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Volumes and issues
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Volume 170 (2024)
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