- Volume 112, Issue 1, 1979
Volume 112, Issue 1, 1979
- Article
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The Bacterial Nucleoid
More LessThis article deals with some aspects of the structure of the nucleoid in Escherichia coli. It is based on a contribution to the symposium on ‘Relations between Structure and Function in the Prokaryotic Cell’ at the Annual Meeting of the Society for General Microbiology in April 1978, but was not published in the Symposium Volume.
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- Biochemistry
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The Binding of Enzymes to Fungal βGlucans
More LessPurified preparations of the extracellular glucan of Sphacelia sorghiand the walls of Claviceps purpurea were shown to contain enzymically active protein. The glucans and walls were treated in various ways to liberate the protein and determine the nature and strength of its binding, if any, to each matrix. Binding of protein to the glucan appeared to be non-covalent and was specific only in that the native protein seemed to bind more firmly than protein derived from other fungal genera. Binding of protein to walls appeared to be stronger than to the glucan but in each case protein was found to be less stable when freed from its carbohydrate matrix. Protein liberated from glucan showed enhanced activity although its K m remained the same; thus, this matrix acted in the same manner as a non-competitive inhibitor. Protein liberated from walls was less active than when attached. The differences between the two matrices, with respect to protein binding, are discussed in the light of possible differences in their tertiary structure.
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Origin of Deoxyuridine Triphosphate in Bacillus subtilis Infected with Bacteriophage PBS1
More LessdCyd deaminase and dUrd kinase did not appear to be important in the synthesis of dUTP in Bacillus subtilis infected with phage PBS1. PBS1 infection did not affect the activities of dCyd kinase, dCyd deaminase, dCMP deaminase and ribonucleotide reductase. dUTP in PBS 1-infected cells was apparently formed by the action of dCTP deaminase induced by PBS 1, by host dCMP deaminase and by host UTP reductase. By labelling the phage DNA with radioactive precursors in hosts carrying various pyrimidine mutations, it was found that about 50% of dUTP was derived from UTP reduction, 30% from dCTP deamination and 20% from dCMP deamination.
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- Development And Structure
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Cell Wall Turnover During Myxospore Formation in Myxococcus xanthus
More LessWall turnover in Myxococcus xanthus has been studied by measuring the incorporation and release of meso-diamino [14C] pimelic acid. The rate of turnover was low in vegetatively growing organisms. Following the addition of 0.5 M-glycerol to induce myxospore formation in organisms that had been labelled for one generation in the absence of glycerol, increased rates of incorporation and release were observed both before and during cellular morphogenesis. Chloramphenicol inhibited glycerol-induced myxosporeformation, but only partially blocked the release of meso-diaminopimelic acid. A mutant, non-inducible by glycerol, was isolated and was found to show no increased autolytic activity in the presence of glycerol. Both parent and mutant strains could be induced to form myxospores by 17 mM-phenethyl alcohol, but with both strains there was only a slight increase in meso-diamino-pimelic acid release following induction.
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- Ecology
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Effects of Azotobacter chroococcum on Barley Seed Germination and Seedling Development
More LessWhen cells or the culture filtrate of Azotobacter chroococcum grown on a medium without a source of fixed nitrogen were added to barley seeds, they sometimes stimulated the extension of seedling roots. The stimulation appeared to be due to a bacterial metabolite as the cells used were non-viable (due to a decrease in pH of the growth medium). There was no evidence that 3-indoleacetic acid or gibberellic acid, which were produced by the bacterium, were involved in the stimulation. When the bacterium was grown on a medium containing nitrate, the cells, but not the culture filtrate, always inhibited germination and the extension of seedling roots. This inhibition of germination appears to be due to competition between viable bacteria and seed for available oxygen.
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Attraction of Nematodes to Living Mycelium of Nematophagous Fungi
More LessMethods were designed to detect attraction and repulsion of nematodes by fungi and determine the attraction intensity of different fungi. Of 23 fungi tested, 15 attracted the bacteria-feeding nematode Panagrellus redivivus. Of the 14 nematophagous fungi tested, ten attracted and one repelled nematodes, whereas three were neutral. Among nine non-nematophagous fungi, five attracted nematodes. In general, the attraction intensity increased with increasing dependence of the fungi on nematodes for nutrients.
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- Genetics And Molecular Biology
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Genetic and Biochemical Studies of Mutants of Penicillium chrysogenum Impaired in Penicillin Production
More LessSeventy-eight mutants of Penicillium chrysogenum strain NRRL 1951, that were impaired in penicillin production, were isolated following treatment with various mutagens. Twelve that yielded about 10% of their parental penicillin titre were studied in detail. Analyses of heterozygous diploids formed between them revealed the existence of at least five complementation groups with respect to penicillin production – V, W, X, Y and Z. Most mutants belonged to group Y. A biochemical investigation of the intracellular peptides in strains representing the five groups demonstrated the absence of the tripeptide α-aminoadipoyl-cysteinyl-valine from mutants of groups X, Y and Z. Extracts of mutants of groups W, Y and Z were able to catalyse a penicillin acyl-exchange reaction, a mutant of group V showed only a trace of activity and a mutant from group X completely lacked this ability.
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Generalized Transduction in Rhizobium leguminosarum
More LessGeneralized transduction in Rhizobium leguminosarum by two virulent bacteriophages, RL38 and RL39, is described. The transduction frequency was increased by ultraviolet irradiation of phage lysates. Cotransduction of auxotrophic and antibiotic resistance markers was shown, as was transduction of two PI group R plasmids. Transduction between strains of Rhizobium trifolii and interspecific transduction from R. leguminosarum to R. trifolii occurred but no transduction from R. trifolii to R. leguminosarum was detected.
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The Pools of Ribosomal Proteins and Ribosomal Ribonucleic Acids During Relaxed Control of Escherichia coli A19 (Hfr, rel met rns)
More LessThe soluble fraction extracted from Escherichia coli A19 (Hfr, rel met rns) during early and late times of phenotypic and genotypic induced relaxed control have been examined for the possible accumulation of ribosomal proteins (r-proteins) and rRNA species during this time of unbalanced macromolecular synthesis. Ribosomal proteins and rRNA species were not found to accumulate within the soluble fraction at any time during this period of relaxed control; even after the typical rRNA accumulation had ceased, r-proteins did not accumulate. It is concluded, from these and related observations, that the r-proteins and rRNA species known to be produced during relaxation must immediately associate to form the unusual ribonucleoprotein particles (e.g. ‘relaxed particles’ and ‘chloramphenicol particles’) characteristic of periods of relaxed control. Since r-proteins do not accumulate even when net RNA accumulation halts, it appears that some elements of the normal, basic co-ordination between rRNA and r-protein synthesis/stability persist even during relaxed control.
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Differences Between the Anthranilate-5-phosphoribosylpyrophosphate Phosphoribosyltransferases of Salmonella typhimurium Strains LT2 and LT7
More LessThe anthranilate-5-phosphoribosylpyrophosphate phosphoribosyltransferases (PRT), coded by the second structural gene (trpB) of the tryptophan (trp) operon in strains LT2 and LT7 of Salmonella typhimurium, differ from each other in a number of parameters. These include the apparent K m values for their substrates anthranilic acid and 5-phosphoribosylpyro-phosphate, thermostability, sensitivity to substrate inhibition by anthranilic acid, as well as end-product inhibition by tryptophan and specific activity. The PRT of strain LT7 further differs from that of strain LT2 in that its apparent K m for 5-phosphoribosylpyrophosphate is three to seven times higher when associated with anthranilate synthase in the enzyme complex which catalyses the first two steps of tryptophan biosynthesis than in its free uncomplexed form, while the PRT of strain LT2 shows the same apparent K m for this substrate in both its free and complexed forms. These results confirm and extend the finding of Stuttard (1975) that strains LT2 and LT7 differ genetically from each other at a single site within region II of the trpB gene.
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- Immunology
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The Preparation and Chemical Composition of Fractions from Aspergillus fumigatus Wall and Protoplasts Possessing Antigenic Activity
More LessA detergent-soluble fraction was prepared from the fragmented wall of Aspergillus fumigatus mycelium using the non-ionic detergent Triton X-100, and a wall-free extract was prepared from the same source in the form of protoplasts, released by a lytic enzyme system from Trichoderma harzianum. These extracts were examined by polyacrylamide gel electrophoresis and their detailed chemical composition was established. They were compared with the water-soluble fraction prepared from total mycelium, which is used routinely in this laboratory for serological tests. All fractions had immunological reactivity towards an antiserum prepared in rabbits against this water-soluble fraction of the mycelium, as shown by double diffusion. Both protein and carbohydrate moieties appear to be involved in the antigenic sites, with carbohydrate reactivity predominantly associated with the protoplast fraction. The fact that all preparations contained at least one common antigenic determinant, as judged by lines of identity to a single antiserum, is discussed in relation to antigen location.
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- Medical Microbiology
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Host Modification of Chlamydiae: Differential Infectivity for Cell Monolayers of Chlamydiae Grown in Eggs and Monolayers
I. Allan and J. H. PearceCell monolayer-grown chlamydiae (CGO) differed from egg-grown organisms (EGO) in their increased spontaneous infectivity relative to centrifuge-assisted infectivity for mono-layers. For each population spontaneous: centrifuge-assisted infectivity ratios were constant over a wide dose range. Spontaneous infection increased linearly with time and could not be exhausted from either population by prolonged adsorption; there was no change in infectivity ratios in residual supernatants. Further, one passage of EGO through monolayers gave CGO with stable infectivity properties not increased by further cell passage yet reverting on a single passage in eggs. Spontaneous infection of monolayers with EGO gave progeny with the same infectivity ratios as monolayers infected with EGO by centrifugation. The change in properties following EGO infection of monolayers occurred prior to natural release from cells. We conclude that EGO and CGO are two phenotypically distinct, homogeneous populations. The two infection modes are not properties of subpopulations within EGO and CGO. The relationship of these observations on chlamydiae to other possible host-imposed phenomena is considered.
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Host Modification of Chlamydiae: Presence of an Egg Antigen on the Surface of Chlamydiae Grown in the Chick Embryo
I. Allan and J. H. PearceEgg-grown chlamydiae (EGO) have a yolk sac antigen associated with their surface which is absent from cell monolayer-grown organisms (CGO). EGO infectivity was specifically neutralized by rabbit antiserum to normal yolk sac; CGO infectivity, before or after incubation with normal yolk sac material, was not neutralized. Treatment of EGO with Clostridium welchii culture filtrate, containing phospholipase C, abolished spontaneous infectivity for monolayers and neutralization by anti-yolk sac antiserum but did not affect centrifuge-assisted infectivity. The possible significance of host antigen on the chlamydial surface is considered.
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- Physiology And Growth
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Characteristics of a Lipolytic and Fatty Acid-requiring Butyrivibrio sp. Isolated from the Ovine Rumen
More LessA naturally occurring fatty acid-requiring Butyrivibrio sp. (strain S2), isolated from the ovine rumen, deacylates plant galactolipids, phospholipids and sulpholipids to obtain sufficient fatty acid for growth. Growth in vitro was promoted by adding to the growth medium a single straight-chain saturated fatty acid (C13 to C18) or vaccenic acid. Patmitoleic and oleic acids also supported growth but gave lengthy lag phases probably due to their toxicity. Linolenic and linoleic acids supported good growth but they were completely hydrogenated to trans-11-octadecenoic acid which was incorporated into the bacterial complex lipids. No chain elongation, chain shortening or desaturation of the added fatty acids occurred and all were substantially incorporated into bacterial lipids of the plasma-logen type, partially as a new type of hydrophobic grouping derived from two molecules of fatty acid. The absence of fatty acid unsaturation poses the question of the maintenance of membrane fluidity within this bacterium.
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Cytology of Sclerotinia sclerotiorum and Related Species
More LessIsolates of Sclerotinia sclerotiorum (Lib.) de Bary, S. trifoliorum Erikss. and S. minorJag. were studied to determine if the numbers of nuclei in mature ascospores and chromosome numbers of these fungi could be used for identification purposes. Isolates of S. minor had four nuclei in each ascospore and a haploid chromosome count of four, S. trifoliorum had four nuclei in each ascospore and a haploid chromosome count of eight, and S. sclerotiorum had two nuclei per ascospore and a haploid chromosome count of eight. Thus, consistent cytological differences were observed, supporting our earlier conclusions that S. minor, S. trifoliorum and S. sclerotiorum are distinct species.
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Carbohydrate Metabolism in Rhizobium trifolii: Identification and Symbiotic Properties of Mutants
More LessCrude extracts of Rhizobium trifolii strain 7000 contained enzymes of the Entner–Doudoroff and pentose phosphate pathways. No phosphofructokinase (EC 2.7.1.11) activity and only a low activity of fructose-1,6-bisphosphate aldolase (EC 4.1.2.13) were found, suggesting that the Embden–Meyerhof–Parnas pathway was not physiologically important in this strain.
Independent carbohydrate-negative mutants of R. trifolii were isolated and characterized as deficient in glucokinase (glk; EC 2.7.1.2), fructose uptake (fup), the Entner–Doudoroff pathway (edp) and pyruvate carboxylase (pyc; EC 6.4.1.1). Glucokinase was essential for glucose phosphorylation in R. trifolii and was also required for growth on sucrose. The edp mutant was impaired in growth on all hexoses tested except galactose, suggesting that the ED pathway was the major pathway used by R. trifolii for the catabolism of these sugars. Galactose may be catabolized via a different pathway, possibly involving an NADP+-linked galactose dehydrogenase. Pyruvate carboxylase was an important anaplerotic enzyme in R. trifolii required for growth on all carbon sources tested, except succinate.
All the mutants, including a glk fup double mutant, formed an effective symbiosis on red clover, suggesting that neither glucose, fructose nor sucrose are used by the bacteroids to provide ATP and reductant for nitrogen fixation. The bacteroids probably receive a supply of tricarboxylic acid cycle intermediates from the plant cytosol, and these may be their major source of energy.
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β-Galactoside Transport in an Alkaline-tolerant Strain of Bacillus circulans
More LessAn alkaline-tolerant bacterium, which grew on various carbohydrates between pH 6 and 9·5, was isolated from soil and identified as Bacillus circulans. Lactose-grown organisms exhibited a transmembrane pH gradient (ΔpH) of −47 mV at pH 6·6, but no ΔpH at pH 9·0. The transmembrane electrical potential (Δψ) was −66 mV at pH 6·6 and −115mV at pH 9·0. Thus the total protonmotive forces at the two pH values were essentially the same. Lactose-grown organisms transported thiomethyl β-D-galactopyranoside (TMG) at pH 6·6 and at pH 9·0, but transport at the alkaline pH was dependent upon addition of ascorbate/N,N,N′,N′-tetramethyl-p-phenylenediamine (TMPD) or preincubation with lactose. In the presence of ascorbate/TMPD, the TMG transport system exhibited similar kinetics and substrate specificities at pH 6·6 and pH 9·0, and resulted in accumulation of chemically unmodified TMG to a concentration approximately 180 times greater than the external concentration. Experiments in which a diffusion potential was generated in starved organisms or in which organisms were treated with nigericin indicated a lack of correlation between the rate of TMG uptake and the magnitude of Δψ. By contrast, the rate of TMG uptake correlated with cellular ATP levels in organisms incubated at different pH values and in organisms treated with N,N′-dicyclohexylcarbodiimide, arsenate or nigericin.
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- Short Communication
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Effect of Piperacillin on D-Alanine Carboxypeptidase Activities from Pseudomonas aeruginosa
More LessMembrane-bound d-alanine carboxypeptidase activity from Pseudomonas aeruginosa is very sensitive to inhibition by piperacillin.
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Studies on the Interaction of Mycobacterium microti and Mycobacterium lepraemurium with Mouse Polymorphonuclear Leucocytes
More LessWhen polymorphonuclear leucocytes (PMN) elicited in mice were infected with Mycobacterium microti or Mycobacterium lepraemurium, phagosome–lysosome fusion occurred with both species. This contrasts with the situation in macrophages where phagosome–lysosome fusion is inhibited by M. microti but not M. lepraemurium. No evidence was found for killing of M. microti or M. lepraemurium when the bacteria were isolated from PMN and their viability tested in cell-free medium or macrophages.
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Glucan-binding Proteins of Streptococcus mutans Serotype c
More LessThree glucan-binding proteins have been isolated from the extracellular fluid of cultures of Streptococcus mutans serotype c. These proteins were adsorbed to glucans containing 1,3-α or 1,6-α bonds and linked to various chromatographic supports: they were eluted from columns by a dextran solution. Glucosyltransferase activity was associated with two of the glucan-binding proteins.
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High and Low Toxin Production by a Non-toxigenic Strain of Clostridium botulinum Type C Following Infection with Type C Phages of Different Passage History
More LessToxin production in Clostridium botulinum types C and D is governed by specific bacterio-phages. Prior passages of a phage controlling type C toxin production caused subsequently lysogenized bacteria to become variably toxigenic. This appears to be one of the causes of the decrease in toxigenicity which is common in some type C and D strains. The morphology of bacteria was also changed from rod-shaped to filamentous by infection with a successively propagated phage.
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- Taxonomy
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Numerical Taxonomy of Actinomadura and Related Actinomycetes
More LessOne hundred and fifty-six Actinomadurastrains, marker strains of related taxa, and related isolates from bagasse and fodder were the subject of numerical phenetic analyses using 90 unit characters. The data were examined using the simple matching (S SM ), Jaccard (S j ) and pattern (D P ) coefficients and clustering was achieved using both single and average linkage algorithms. Cluster composition was not markedly affected either by the coefficient or clustering algorithms used or by test error, estimated at 4·5 %. Actinomadura dassonvillei, Actinomadura madurae and Streptomyces somaliensis formed good taxospecies, but the separation of Actinomadura pelletieri strains into two clusters by S j and S sm analysis requires further study. The single representatives of Actinomadura helvata, Actinomadura pusilla, Actinomadura roseoviolacea, Actinomadura spadix and Actinomadura verrucosospora seemed to form new centres of variation while Actinomadura citrea and Actinomadura malachitica showed much similarity with Actinomadura madurae. Most of the isolates from bagasse and fodder were recovered in two well-defined phena, provisionally labelled clusters ‘A’ and ‘B’which showed little similarity to either Actinomadura or Nocardia strains. The effect of the different coefficients on the aggregation of clusters is discussed.
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