- Volume 46, Issue 1, 1967
Volume 46, Issue 1, 1967
- Obituary
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- Article
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The Inhibition of the Growth of Clostridium welchii by Lipids Isolated from the Contents of the Small Intestine of the Pig
R. Fuller and J. H. MooreSUMMARYThe growth of Clostridium welchii type A NCTC 8246 was inhibited by the contents of the small intestine of pigs from which food had been withheld for 24 hr ; no inhibitory activity was observed by the contents of the stomach, caccum and large intestine. Inhibitory activity was absent from the contents of the small intestine during the early stages of digestion but first appeared about 6 hr after the pigs had been given food. This indicated that under normal feeding practice there were periods during each day when the contents of the small intestine would be inhibitory for C. welchii. The inhibitory activity was in the lipid fraction of the intestinal contents. Fractionation of the intestinal lipids showed that the inhibitory substances were linoleic and arachidonic acids, lysolecithin and an unidentified phospholipid. The poly-unsaturated fatty acids and lysolecithin appeared to be derived mainly from the action of pancreatic phospholipase A on biliary lecithin in the lumen of the small intestine. The possibility that these inhibitory lipids control to some extent the numbers of C. welchii in the alimentary tract of the pig is discussed.
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Observations on the Weissensee g Strain of Corynebacterium diphtheriae
More LessSUMMARYFrom a Park-Williams No. 8 strain (Weissensee g) of Corynebacterium diphtheriae, recently reported by Rajadhyaksha & Rao (1965) to be toxinogenic but non-lysogenic, two diphtherial strains have been isolated : 1, a typical phage-resistant, slow-growing, toxinogenic pw8 strain; 2, a fast-growing non-toxinogenic strain that is sensitive to diphtherial phages.
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Methionine synthesis in Proteus mirabilis
More LessSUMMARYSixty different isolates of methionineless auxotrophs of Proteus mirabilis were arranged in nine biochemical groups according to their growth responses to methionine or its precursors. These requirements suggested that P. mirabilis possesses a route for methionine biosynthesis which is similar to the pathway operating in Escherichia coli and Salmonella typhimurium. In contrast to findings with the latter organisms syntrophism was not observed between these mutants of P. mirabilis even with sonically disrupted potential feeder strains. Two methionineless auxotrophs of E. coli fed auxotrophs of P. mirabilis which had metabolic blocks earlier in this pathway. These results, which suggested an inability of methionineless auxotrophs of P. mirabilis to accumulate precursors of metabolic blocks, were confirmed by a quantitative comparison of methionine precursors in wild-type and mutant strains of P. mirabilis and E. coli. The presence of S-methylcysteine (SMC) was demonstrated in wild-type and methionineless auxotrophs of P. mirabilis and E. coli. The growth responses of methionineless auxotrophs of P. mirabilis to SMC supported a hypothesis for the participation of this amino acid in the synthesis of methionine via an alternative route.
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Incorporation of 3H-Uridine into RNA during Cellular Slime Mould Development
More LessSUMMARYDictyostelium discoideum wild-type amoebae incorporate 3H-uridine into RNA at a linear rate during the developmental sequence until the terminal stage of fruiting body construction. However, 3 aggregateless strains perform in similar fashion (except for the final decrease). A sensitive criterion of bacterial contamination, making use of MAK-column chromatography of the labelled RNA, is described.
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The Metabolism of Triglycerides by Spores of Penicillium roqueforti
More LessSUMMARYThe ability of suspensions of washed spores of Penicillium roqueforti to oxidize triglycerides was markedly stimulated by l-proline, l-alanine and l-serine, although all the sources of nitrogen tested were effective over extended periods to different degrees. The rate of oxidation was further increased by the addition of certain sugars, although these were without effect in the absence of a nitrogen source. The same compounds that stimulated methylketone formation from triglycerides also promoted the rapid germination of spores, suggesting that common reactions were involved. The maximum yield of methylketone obtained was 25 % from trioctanoin and trihexanoin at pH 6·0, with lower yields from tridecanoin, tributyrin and trilaurin. The addition of sodium azide, and to a lesser extent of 2,4-dinitrophenol and certain organophosphours compounds, inhibited the oxidation of triglycerides. The possible role of fungal esterases in spore germination is discussed.
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The Spore-Surface Depsipeptide of Pithomyces sacchari
More LessSUMMARYThe spore-surface spicules of Pithomyces sacchari contain the cyclotetra-depsipeptide, angolide.
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Associated Diploids Involving Penicillinase Plasmids in Staphylococcus aureus
More LessSUMMARYStaphylococcus aureus penicillinase plasmid diploids of the type (α. i+p+ A/β.i–pC+), when constructed in strain 147, normally segregated one of the two parental genotypes at a frequency of about 1/5000 divisions, and recombinants were rare. In about 2% of the diploid clones, however, segregation occurred at a much higher frequency and in these clones both plasmids might be lost together. Examination of these ‘unstable’ diploids suggests that their two plasmids are associated to form a single structure, so that they are subsequently lost or transduced together. The ease of formation of associated diploids suggests that the penicillinase plasmids may be circular.
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Studies on the Effects of Aerosolization on the Rates of Efflux of Ions from Populations of Escherichia coli Strain b
More LessSUMMARYPotassium and phosphate were found to be the most suitable of the common ions for investigations into a possible correlation between ion movements and survival in populations recovered from aerosols of Escherichia coli strain b. Except at high relative humidities and short holding times, populations of [43K]-labelled E. coli lost practically all the radioisotope within a very short time after recovery from bacterial clouds. Very little [43K] was removed from labelled bacteria by agitation in water or buffer solutions under conditions which simulated some of the stresses arising from the generation and collection of aerosols. Loss of potassium appeared to be a sequel of aerosolization, but was not in itself immediately lethal to the organisms. However, the results indicated that organisms which had been recovered from aerosols could not be regarded as unchanged rehydrated forms of the original bacteria. The pattern of phosphate efflux from [32P]-labelled organisms was quite different from the corresponding loss of potassium. A great deal of phosphate loss was due merely to the violent ‘washing’ procedures involved in the generation and collection of aerosols. Damage to ion-retention mechanisms may contribute to the decreased viability of organisms recovered from bacterial aerosols.
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Some Observations on the Envelope of an Influenza Virus
More LessSUMMARYMicrographs of the envelope of fowl-plague virus revealed an arrangement of subunits each one of which was surrounded by either five or six others. The similarity of this arrangement to that of a cubic virus capsid has led us to consider which components of morphologically different viruses fulfil similar functions.
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The Aliphatic Acylamide Amidohydrolase of Mycobacterium smegmatis : Its Inducible Nature and Relation to Acyl-Transfer to Hydroxylamine
More LessSUMMARYMycobacterium smegmatis nctc 8159 grew well in a minimal medium with succinate or acetamide as sole carbon source. Washed bacteria or cell-free extracts hydrolyzed 15 monocarboxylic amides, but not 4 related N-substituted amides. Formamide was the best substrate, followed by n-butyramide. Extracts of bacteria grown on acetamide hydrolyzed formamide about 60 times and butyramide about 20 times as rapidly as bacteria grown on succinate. Other short-chain fatty acylamides were also more rapidly hydrolyzed, but benzamidase activity was not similarly induced by growth on acetamide. Extracts of bacteria grown on succinate transferred acyl groups from propionamide, butyramide and nicotinamide to hydroxylamine, to form hydroxamates. Transferase activity, unlike aliphatic amidase activity in extracts was purified twofold and freed from transferase activity. Formamidase and butyramidase activities were not separated, and were similarly affected by heat and dithio-bis-nitrobenzoic acid. The amidase was induced by growth on acetate and on butyramide, but not on propionate, butyrate or benzamide, all of which were good growth-substrates. N-methylacetamide and N-acetyl-acetamide were non-substrate inducers of amidase for bacteria growing on succinate.
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Effect of Food Intake on Growth and Survival of Salmonellas and Escherichia coli in the Bovine Rumen
More LessSUMMARYWhen salmonella organisms were put into the rumen of cattle their subsequent growth or elimination depended on the dietary intake before and after the organisms were ingested. When the animals were receiving a regular daily ration of 6·8 kg. lucerne hay the organisms were rapidly eliminated from the rumen and viable organisms in the faeces were rarely detected. Decreasing the daily food intake to 2·3 kg. or interruption of feeding for one or more days retarded the elimination of salmonellas and Escherichia coli or permitted their growth in the rumen. Growth of salmonellas and E. coli type I occurred during starvation, and resumption of feeding after starvation caused further multiplication. Starvation for 2 or 3 days was generally followed by infection of the intestine, with salmonellas persisting in the faeces for at least a week.
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The Fine Structure of the Mature Zoosporangium of Nowakowskiella profusa
More LessSUMMARYThe fine structure of the mature sporangium of Nowakowskiella profusa Karling (Chytridiales, Phycomycetes) is described. Deductions are made about the dehiscence mechanism and the nature of the zoospore. A striking feature of the zoospore is a conspicuous fibrous body immediately adjacent to the refractive globule. This body possibly represents a primitive photoreceptor organelle.
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Cereolysin : Production, Purification and Partial Characterization
More LessSUMMARYA method is described for production of the extracellular haemolytic growth-product of Bacillus cereus. The lytic substance, called ‘cereolysin’, can be purified by fractional precipitation with ammonium sulphate, density-gradient electrophoresis and gel filtration. The purified material is a labile protein of molecular weight about 52,000. It has a very high order of haemolytic activity, is lethal for mice, and resembles streptolysin O in being inhibited by cholesterol, but differs from streptolysin O in other respects.
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Sensitivity of Streptomycetes to Antibiotics as a Taxonomic Character
More LessSUMMARYA procedure for testing the sensitivity of streptomycetes to antibiotics is described. Eight antibiotics, at various concentrations, were incorporated into filter-paper discs and by selection of suitable concentrations results of diagnostic value were obtained. Streptomycetes previously grouped together by using other criteria had identical or very similar antibiotic sensitivity patterns. It is considered that the reactions of streptomycetes to a range of antibiotics would be of value for description of species and studies of overall similarity.
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