- Volume 24, Issue 3, 1961
Volume 24, Issue 3, 1961
- Article
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Virolysin, a Virus-Induced Lysin: Its Appearance and Function in Phage-Infected Staphylococci
More LessSummary: The formation and role of enzyme, virolysin, in Staphylococcus aureus K1 infected with phages P1 and P14 are described. Virolysin is a by-product of the metabolism of the cell which is actively producing phage, not of the normal cell. Virolysin is first detected within 10-15 min. in a 40–50 min. latent period and increases linearly until lysis. Normal cell autolysin remains constant during infection. Observations on lysis and phage release show that (1) certain inhibitors which prevent lysis of the cocci by external virolysin also prevent lysis and phage release when added at the end of the latent period; (2) the rate of premature lysis of, and phage release from, cocci chilled during the latent period depends upon their virolysin content. Both observations suggest that virolysin functions in phage release.
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A Protein Factor in the Nutrition of Paramecium caudatum
More LessSummary: The ciliate Paramecium caudatum was cultivated in a medium consisting principally of known chemical compounds, including 17 amino acids, guanylic, adenylic, cytidylic and uridylic acids, sodium acetate and sodium pyruvate, linoleic and oleic acids, a mixture of B vitamins and several inorganic salts. In addition it was necessary to add microgram quantities of a protein concentrate, first obtained from autolysed yeast, but recently by an improved method from dried green peas. Lipids were first extracted from the crude material and the protein was then dissolved and precipitated with 10% trichloroacetic acid. This protein was further purified by paper chromatography to yield a concentrate active in dilutions as low as 10 μg./ml. When the protein was hydrolysed enzymically or by acid or alkali, the hydrolysates were inactive. Sixteen amino acids were qualitatively identified in the hydrolysate. The nutritional role of a protein effective in such small concentrations has not yet been satisfactorily explained.
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Some Aspects of the Genetics of Methionineless Mutants of Salmonella typhimurium
More LessSummary: Forty-six methionineless mutants of Salmonella typhimurium were arranged in three phenotypic groups according to their growth responses to potential precursors of methionine. The results of syntrophism tests led to the recognition of two more phenotypic groups and permitted the arrangement in sequence of the metabolic steps in which mutants of each of the five groups were deficient. Transduction experiments indicated that each of these groups comprised mutants whose sites of mutation were closely linked within a complex locus. Attempts to map the sites of mutation of 12 mutants within one locus were unsuccessful. One of the mutants, probably a deletion, failed to recombine with the other 11 and behaved differently from them in linked transduction. A group of three and one pair of the 11 mutants could not be separated by recombination. Linkage was detected by transduction between only 2 of the 5 loci; these were concerned with non-sequential steps in the biosynthesis of methionine. No linkage was detected between the methionine loci and any of a number of other loci, including those controlling the biosyntheses of cysteine and tryptophan. These results were only partly in accordance with a previously suggested linkage map.
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Phenotypic Alterations Associated with the Bacteriophage Carrier State of Shigella dysenteriae
More LessSummary: Shigelladysenteriae strain 136-R4 is lactose-negative, mannitol-negative (Lac−Mann−) and is sensitive to bacteriophage T7. Carrier clones of strain R4 (contaminated with T7) were found to maintain their association with phage T7 through as many as fifty consecutive single-colony isolations (from an ancestral colony which had survived lysis by phage T7). All carrier cultures (so-called pseudolysogenic strains) were found to be lactose-positive and mannitol-positive (Lac+ Mann+). Passage of Lac+ Mann+ bacteria through media containing antiserum directed against phage T7 resulted in a change back to Lac− Mann− and in the complete elimination of phage T7.
Biochemical, genetic and immunochemical evidence indicates that the change from Lac− Mann− to Lac+ Mann+ is the result of a phage-controlled alteration in the phenotype of Shigelladysenteriae. This dysentery bacillus is cryptic with respect to the expression of Lac+ Mann+ and the crypticity is attributable to surface structures (which are probably not a part of the Y or permease system). Under appropriate conditions decryptification may be brought about by phage-associated endolysin. Similar phenomena were observed in carrier strains of certain other members of the Enterobacteriaceae.
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Stimulation of Streptomycin-Resistant Bacteria in the Rhizosphere of Leguminous Plants
More LessSummary: Bacteria which were resistant to streptomycin and rose bengal were preferentially stimulated in the rhizospheres of several plant species as compared with those in the soil away from the rhizosphere. Leguminous plants were the most effective and clover plants as young as 6 days had some effect. The separate and combined effects of rose bengal and streptomycin in the isolation medium were examined. Rose bengal alone had little effect on bacterial numbers, whereas streptomycin alone decreased them. The two substances together affected rhizosphere numbers strikingly but inconsistently. The bacteria from rhizosphere and soil were grouped according to their nutritional requirements. Chromogenic bacteria with simple requirements were the most abundant forms resistant to streptomycin + rose bengal in the rhizosphere and a species of Flavobacterium was especially favoured.
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Chemical and Metabolic Properties of Various Elements Found in Cultures of a Stable Proteus L Form
C. Weibull and H. BeckmanSummary: The microscopic elements which constituted cultures of a stable L form (Proteus L9) were found to be highly heterogeneous with respect to morphological, chemical and metabolic properties. The smallest elements found in the cultures studied (diameter < 0·3 μ) contained more lipid-phosphorus (lipid-P), but less ribonucleic acid-phosphorus, deoxyribonucleic acid-phosphorus and protein-nitrogen, than whole cultures consisting predominantly of bodies of diameter > 1 μ. The small elements respired at about the same rate as whole cultures, but they showed low, if any, biosynthetic activity. The small elements probably possess a structural organization similar to that of L bodies of larger sizes, but most of them contained little, if any DNA.
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The Effect of Temperature on the Production by Coagulase-Positive Staphylococci of Staphylokinase and other Extracellular Substances
More LessSummary: Three strains of coagulase-positive staphylococci, grown at temperatures between 35° and 43°, showed no significant change in mass of growth or in yield of α-haemolysin and the Panton-Valentine (PV) leucocidin. Staphylokinase production, however, decreased by 18% (per mg. dry weight) for each degree rise in temperature. The amount of hyaluronidase produced at 37° was five to eight times greater than that produced at 41°.
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Experimental Conditions for Nitrate Reduction by Certain Strains of the Genus Lactobacillus
More LessSummary: Costilow & Humphreys’s (1955) observation that certain strains of Lactobacillus plantarum reduced nitrates under certain conditions was confirmed. Two strains of L. fermenti also reduced nitrates. In static culture, agar and anaerobiosis were not essential for nitrate reduction, contrary to speculations in the literature. Nitrate reduction was possible only in media with restricted carbohydrate and with the pH value maintained at a relatively high value within the activity range of nitrate reductases. For good growth, lactobacilli for the nitrate test have been customarily grown in media with high carbohydrate content, with consequent low final pH values. This seems to be the essential reason why the genus Lactobacillus had previously been defined as unexceptionally nitratase-negative.
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Purification and Properties of Neuraminidase from Vibrio cholerae
More LessSummary: A method is described for the purification of neuraminidase from culture fluids of Vibrio cholerae. Five steps are involved: fractionation with methanol, adsorption to and elution from human red cells, fractionation with ammonium sulphate, chromatography on columns of hydroxyl apatite, crystallization. From 35 l. of culture filtrate, an average yield of 21% of the original enzyme activity was obtained as crystals. The degree of purification was about 5000 fold. Purified neuraminidase possessed 12·6 × 106 units of biological activity/mg. dry weight, and gave a value for E 1% 28 mμ of 8·96, measured at 0·025% (w/v). Enzyme activity was stimulated by calcium ions and inhibited by ethylenediaminetetra-acetate. In the presence of 0·001 m-CaCl2, neuraminidase showed maximum activity at pH 5·6. With sialyl lactose as substrate, a value of 1·2 × 10−3 m was found for the Michaelis constant. At an enzyme concentration of 0·16 μg./ml., V max. was 0·021 μ m N-acetylneuraminic acid/min./ml. The enzyme was stable when dried from the frozen state and stored under vacuum at 0°. A suspension of crystals in water also retained activity when stored at 0°. Solutions of crystalline neuraminidase showed a small increase in activity when stored at 0° for several weeks. This effect was greatest at pH 6·7 and 8·5 but was barely detectable at pH 4·6. At pH 5·6 or 6·7, the enzyme lost about 20% of its activity over a period of 2 hr. at 37° (concentration = 15 μg./ml.) No proteolytic activity nor N-acetylneuraminic acid aldolase activity was detected in the crystalline preparation.
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Electrophoretic, Sedimentation and Diffusion Behaviour of Crystalline Neuraminidase from Vibrio cholerae
J. Pye and C. C. CurtainSummary: Crystalline neuraminidase prepared from Vibrio cholerae culture fluids by Ada, French & Lind (1961) was examined by moving boundary electrophoresis, analytical ultracentrifugation and diffusion. The various corresponding physical constants were obtained. The results indicated that, within the limits of the methods used, the crystalline protein was enzyme and was homogeneous.
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Morpholoǵical Variation in Spirillum spp., with Observations upon the Origin of the Hyphomicrobia
More LessSUMMARY: Pure cultures of Spirillum serpens grown on solid medium contained variants of very diverse morphological appearance; these were relatively straight rods, and branched coccobacillary and coccal forms. Flagella were in the normal lopho-trichous arrangement, peritrichous, single or absent. Some forms possessed characters resembling those of the hyphomicrobia. The development of Rhodomicrobium in cultures of photosynthetic spirilla was also observed. It is suggested, not only that the spirilla possess potentialities consistent with a suggested role as the ancestral bacterial type, but also that Rhodomicrobium may be a growth form of a photosynthetic spirillum. Appearances found in the parasitic Hyphomonas polymorpha and in certain pleuropneumonia-like organisms were considered to support this concept.
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