- Volume 69, Issue 3, 1971
Volume 69, Issue 3, 1971
- Biochemistry
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Properties of Isoleucine Hydroxamate-resistant Mutants of Serratia marcescens
More LessSUMMARY: Isoleucine hydroxamate-resistant mutants of Serratia marcescens have been isolated. Biochemical examination of the isoleucine-valine biosynthetic enzymes allowed the mutants to be grouped into three classes: I, mutants with increased enzyme levels; II, mutants with feedback inhibition-insensitive l-threonine dehydratase; III, mutants without any alteration in either feedback inhibition or enzyme levels. Of these mutants, class II accumulated isoleucine outside the cells in medium containing l-threonine. Strain IHr3i3, whose l-threonine dehydratase was about 500-fold less sensitive to feedback inhibition when compared with wild-type enzyme, accumulated up to 7 mg. of isoleucine per ml. of medium.
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Asparaginase and Glutaminase Activities of Bacteria
More LessSUMMARY: A test-tube method is described for the determinations of l-asparaginase and l-glutaminase in suspensions and extracts of bacteria. An automated modification of the method was used to determine the asparaginase activities of about 200 strains from 78 species and the glutaminase activities of 46 strains from 13 species. Both enzymes were widely distributed and, at pH 8·5, asparaginase was generally the more active. Asparaginase was exceptionally active in some species of Erwinia.
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Pyruvic Acid and Formic Acid Metabolism in Sarcina ventriculi and the Role of Ferredoxin
More LessSUMMARY: Sarcina ventriculi produced hydrogen, CO2 and acetyl phosphate from pyruvate by a clostridial-type thioclastic reaction which required coenzyme A and ferredoxin for activity. Hydrogen production from formate did not require ferredoxin since crude formate hydrogenlyase preparations functioned when depleted of ferredoxin.
With fractionated components of the enzymic system, ferredoxin or viologen dyes restored activity. No evidence for the presence of a coliform-type thioclastic reaction (pyruvate-formate lyase) was found. Reduction of NADP by hydrogen or formate was ferredoxin-dependent. Acetaldehyde and CO2 were produced from pyruvate by a yeast-type decarboxylase which required thiamine pyrophosphate and Mg2+ ions for activity. Extracellular pH influenced the pathways of pyruvate metabolism which were reflected by the molar growth yields for glucose; the thioclastic reaction was predominant at alkaline pH.
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Haem Biosynthesis from [14C]-δ-Aminolaevulinic Acid in Laboratory-grown and Root Nodule Rhizobium lupini
More LessSUMMARY: Both laboratory-cultured bacteria and the bacteroid forms of Rhizobium lupini (strain wu8) isolated from serradella root nodules synthesize haem from [14C]-δ-aminolaevulinic acid (ALA) and release the product into the incubation medium. Laevulinic acid, an inhibitor of haem synthesis in other organisms, effectively inhibits this synthesis in Rhizobium. When compared on the basis of fresh weight, protein or numbers, the laboratory-grown bacteria are more active in the incorporation of [14C]-ALA than are the bacteroid forms, either when intact or when disrupted by sonication. A synergistic effect between cytoplasmic (plant) and particulate (bacteroid) extracts from serradella nodules is observed which is greater than that for soybean nodules. It is proposed that the haem synthesis for leghaemoglobin in serradella root nodules is a co-operative effort between plant and bacteroid.
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Trisporic Acid Production by Blakeslea trispora and its Promotion by Barbiturate
More LessSUMMARY: Defined procedures for the production of trisporic acids in laboratory-scale cultures of mixed plus and minus Blakeslea trispora, and specific assay procedures, are described. Increases in carotenoid and steroid synthesis in such cultures were observed when phenobarbitone was added to the medium; the effect was mainly due to an increase in trisporic acid yields, which in turn is ascribed to the induction of higher levels of mixed function oxygenase enzymes by the barbiturate.
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- Development And Structure
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The Walls of Mycobacterium lepraemurium: Chemistry and Ultrastructure
More LessSUMMARY: Methods are described for isolating the walls of the intracellular parasite Mycobacterium lepraemurium in good yields. The walls were treated with solvents and reagents and their effects were followed by chemical analyses and electron microscopy. The walls resemble those of other mycobacteria, consisting of muco-peptide, arabinogalactan and ester-linked lipid. The lipid forms the outer, electron-transparent layer of the wall. The information available so far offers no explanation of the bacterium’s outstanding resistance to destruction by phagocytic cells.
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- Ecology
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Discharge of Conidia of Entomophthora thaxteriana Petch from the Pea Aphid Acyrthosiphon pisum Harris
More LessSUMMARY: At 21°, conidia of Entomophthora thaxteriana were first discharged from infected pea aphids about 6 to 9 h. after the aphids died and the rate of discharge was highest during a short period about 9 h. later. In constant light, the rate then decreased and discharge ended about 36 h. after an infected aphid died; in constant darkness the maximum rate (2 × 103 conidia/h./aphid) was only one-quarter of that in constant light but it was maintained for 10 h. In alternating 12 h. light, 12 h. darkness, the rate of conidium discharge increased substantially 2 h. after the admission of light and much decreased 2 h. after light was excluded. In constant light, the average number of conidia discharged from one adult apterous aphid was at least 105, twice that in constant darkness. Discharge of conidia began earliest at 20° but the rate of discharge was highest at 25°. Ultimately, similar numbers of conidia were discharged at any temperature from 5 to 25°; conidia were not discharged at 0 or 30°.
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- Genetics And Molecular Biology
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A New Salmonella typhimurium DNA Host Specificity
More LessSUMMARY: The genetic properties of a new (hspS) host specificity of Salmonella typhimurium were investigated using bacteriophage L. Phage L is a better substrate for s-specific restriction than phage P22. Mutants deficient in s-restriction only were found at the same frequency as mutants deficient in both restriction and modification. Crosses between S. typhimurium Hfr and S. typhimurium F− or between Escherichia coli and S. typhimurium showed that the s system has the same chromosomal location as the k system of E. coli. The s system was introduced into E. coli and found to be effective on phage λ.
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Genetic Control of Fertility in Streptomyces coelicolor A3(2): Plasmid Involvement in the Interconversion of UF and IF Strains
More LessSUMMARY: if (Initial Fertility) strains of Streptomyces coelicolor A3(2) are shown to harbour a plasmid (SCP 1). Loss of SCP 1 results in a change of fertility from if to the previously described uf (Ultra-Fertile) type. Although uf × if crosses yield recombinants for chromosomal markers with a frequency of the order of 10−5 of the total progeny, virtually all the progeny carrying the markers of the uf parent are converted to if, by reinfection with SCP 1. Efficient conversion of uf to if in such crosses is associated with the development of aerial mycelium. It is inferred that SCP 1 is responsible for the production of a diffusible substance by if strains, which prevents the development of aerial mycelium by uf strains.
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Absence of Polar Effect of Frameshift Mutations in the E Gene of the Escherichia coli argECBH Cluster
More LessSUMMARY: Four arginine auxotrophs have been obtained in Escherichia coli k12 following treatment with the acridine half-mustard ICR 191. Their properties show that they carry mutations in the E gene of the argECBH cluster, and their reversion patterns indicate that these mutations are frameshifts. The mutations exert no polar effect on the expression of the argC, B and H genes. These results accord with earlier suggestions that E is not transcribed on to the same messenger RNA molecule as C, B and H.
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High-frequency Gene Transfer in Pasteurella pseudotuberculosis
More LessSUMMARY: A high-frequency donor strain of Pasteurella pseudotuberculosis group A was isolated from a strain which had previously accepted an F′lac episome from Escherichia coli. This donor transferred a variety of genetic markers to P. pseudotuberculosis group A recipients. Transfer frequencies of approximately 10−2/donor bacterium were obtained for early markers from membrane matings at 28°; these frequencies were increased to about 2·5 × 10−1/donor at 37°. Recombinant colonies obtained from membrane matings were free from donor and recipient bacteria but some colonies had more than one recombinant class present. The graded frequencies of marker transfer obtained together with recombinant analysis suggest that markers were transferred linearly.
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- Physiology And Growth
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Regeneration of Aspergillus nidulans Protoplasts
More LessSUMMARY: The process of regeneration of mycelial protoplasts from Aspergillus nidulans wild-type and strain P76 has been investigated. In liquid media two patterns of regeneration were observed. In the first, the protoplasts produced chains of yeastlike cells and eventually the terminal cell produced a hypha. In the second wall ‘shells’ were formed into which the cytoplasm migrated. It is suggested that the mechanism of regeneration reflects the site of origin of the protoplast from the parent hypha.
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A Comparison of Respiratory Processes in Spirillum volutans, Spirillum itersonii and Spirillum serpens
More LessSUMMARY: Respiratory processes in Spirillum serpens and S. itersonii were compared with those in the microaerophile S. volutans. Rates of oxygen consumption with various substrates and the catalase activity were lower in S. volutans. The activities of five citric acid cycle enzymes and reduced nicotinamide adenine dinucleotide oxidase in cell-free extracts were also 10-to 200-fold lower. The concentration of cytochrome c was greater in the oxygen-insensitive spirilla. This may explain the poor growth of S. volutans: it is unlikely that the complete inhibition of growth in aerated cultures is due to a haemoprotein deficiency.
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The Influence of Dissolved Oxygen on Pseudomonas am1 Grown on Methanol in Continuous Culture
More LessSUMMARY: Methanol-limited cultures of Pseudomonas ami were grown in chemostats (D, 0·1 h.−1; methanol 10 g./l.) at dissolved oxygen tensions between 1 and 690 mm. Hg. Decreasing the dissolved oxygen tension from no to 28·5 mm. Hg did not affect either respiration or carbon balance, but lowering it further caused a progressive increase in respiration which was maximal at 3 mm. Hg (the lowest dissolved oxygen tension at which a steady state could be maintained at the fixed dilution rate). Increasing the dissolved oxygen tension from 97 to 560 mm. Hg increased production of CO2 and decreased yield; this effect was particularly evident between 420 and 560 mm. Hg. Yield varied little between 560 and 690 mm. Hg but CO2 output decreased and exocellular products increased in concentration indicating a metabolic change. The possible mechanisms involved in metabolic regulation are discussed; it is concluded that dissolved oxygen tensions between 3 mm. and 690 mm. Hg exert a continuous quantitative control over respiration and metabolism of growing organisms. A stoichiometric equation is derived for the growth of Pseudomonas am i on methanol.
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- Society For General Microbiology: Proceedings
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- Short Communications
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- Books Received
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- Corrigendum
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