- Volume 11, Issue 1, 1954
Volume 11, Issue 1, 1954
- Article
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Reduction of Ferric Compounds by Soil Bacteria
More LessSUMMARY: Reduction of ferric lactate by washed cell suspensions of Bacillus circulans, B. megaterium and Aerobacter aerogenes takes place in the presence of suitable hydrogen donors. Ferric hydroxide is reduced when αα′-dipyridyl is present in the cell+substrate system. The reduction of ferric compounds by washed cells+substrate is similar to the reduction of methylene blue. Culture fluids of B. circulans do not reduce ferric iron in the absence of normal cells.
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Tryptophan Metabolism and its relation to Phage Resistance in Escherichia coli
More LessSUMMARY: A scries of phage-susceptible tryptophan-requiring mutants of Escherichia coli, strain B, were found to fall into five distinct phenotypes as determined by their alternate growth response to anthranilic acid and indole, and by the substances which they accumulated in the culture fluids. An unidentified substance partially characterized by colorimetric reactions and absorption spectrum accumulated in the culture fluid of two of these types. Tryptophan-requiring T1 phage resistant mutants (B/1, trp) which were readily obtained by phage selection could not be isolated by the penicillin method. This mutant represents a unique tryptophanless phenotype, not only in terms of its resistance to T1 phage, but also on the basis of: (1) accumulation of a new metabolic product; (2) growth stimulation by histidine and tyrosine; (3) suppression of accumulation of certain metabolic products by the other tryptophan auxotrophs; (4) epistatic expression of phenotype when superimposed on the tryptophan auxotrophs by secondary mutation.
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Enzymes concerned with Gas Formation by some Coliform Bacteria
More LessSUMMARY: The absence of gas produced by certain coliform organisms during growth at elevated temperatures is not a result of an interference with the enzymes concerned, but rather an interference with the mechanism which brings about the appearance of these adaptive enzymes. A reconsideration of some of the evidence tends to support the view that formic hydrogenlyase is a separate entity, distinct from hydrogenase and formic dehydrogenase.
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Genetic Investigation of the Inhibition by dl-Norleucine of the K-12 Strain of Escherichia coli
More LessSUMMARY: The genetic relationship to other markers of the locus for inhibition of K-12 strain of Escherichia coli by norleucine has been investigated. The results showed little or no linkage with the loci for methionine, leucine, threonine or thiamine synthesis, but a close association was found with the Gal5 − and Arab− loci of strain W-677.
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Isolation of Nutritional Mutants of Neurospora crassa by Filtration Enrichment
More LessSUMMARY: Nutritional mutants of Neurospora crassa may be isolated by incubation of microconidia in a liquid medium deficient in specific growth factors followed by fitration and then growth on supplemented media of the conidia remaining in the filtrate.
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A Study of the Diffusible Lipase produced by Staphylococci and of its Immunological Activity
More LessSUMMARY: A systematic investigation of eighteen genera showed that staphylococci were the only potentially pathogenic group which produced a diffusible lipase detectable on solid culture medium. This lipase was obtained in filtrates of cultures grown by a well-established method for preparing staphylococcal toxins. When titrated, filtrates of very active strains showed lipolytic activity in dilutions of 1/4096, but the majority of strains had a titre of 1/256.
Whole cultures and culture filtrates of albus strains and formolized fitrates of aureus strains were found to stimulate the production of anti-lipolytic antibody in rabbit serum. The titre of the most active antiserum was 1/40, and that of the majority 1/10. Each antiserum prepared showed maximal neutralizing activity against the homologous fitrate, but all antisera studied neutralized heterologous filtrates to some extent. No evidence of naturally occurring anti-lipolytic antibody was found in any of the rabbit sera used.
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The Deoxyribonuclease of Typhoid Bacilli and its Effect on Typhoid Bacteriophage Nucleic Acid
More LessSUMMARY: Deoxyribonuclease (DNase) was found in extracts of a strain of Salmonella typhi. Its action on herring sperm deoxyribonucleic acid (DNA) is catalysed by magnesium ions. Calcium ions, although inactive alone, increase the magnesium-catalysed activity of the enzyme. A highly polymerized specimen of phage DNA was prepared by treatment of the purified phage with strong urea solution to dissolve the protein coat. This nucleic acid is degraded by the typhoid DNase in the presence of magnesium. As with herring sperm DNA, calcium is inactive alone but increases the action of magnesium. Calcium is required for multiplication of the phage in the host bacterium, but the hypothesis that the calcium is required to catalyse the breakdown of phage DNA by bacterial DNase was not upheld.
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Nuclear Division and the Life Cycle in a Streptomyces sp
More LessSUMMARY: The life cycle of a Streptomyces sp. was studied by the Robinow HCl-Giemsa method of nuclear staining, and is described in the following manner: (1) initial nuclear division phase; (2) primary mycelium; (3) secondary mycelium (including aerial); (4) the formation of spores. It was observed that the method of nuclear division in the ungerminated spores closely resembled mitosis of certain higher organisms and lower plants, by the appearance of two terminal bodies whose behaviour was similar to mitotic centrosomes. The primary mycelium developed after the initial nuclear division phase and produced side branches, then later gave rise to single swellings in the hyphae. These swellings grew to form large round cells, each of which contained many nuclei. It was from these cells that the secondary mycelium developed, a part of which became aerial and terminated in the form of chains of uninucleate spores.
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A Ninth Variety of Paramecium aurelia
More LessSUMMARY: A new variety of Paramecium aurelia—variety 9—containing two mating types XVII and XVIII, has been identified from seven samples of water collected in Scotland. Variety 9 belongs to the group A varieties in the Sonneborn system of classification, but shows no interparietal mating reactions.
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The Distribution of Polysaccharide Production in Aerobacter and Escherichia Strains and its relation to Antiǵenic Character: With a note on the Influence of Potassium Deficiency upon Production of Polysaccharide by Aerobacter aerogenes
More LessSUMMARY: Strains of Aerobacter aerogenes, A. cloacae and Escherichia coli, including mucoid capsulate, mucoid non-capsulate, smooth and rough variant forms, were grown on defined agar media. The polysaccharide content of the cultures was estimated by the anthrone method and related to the amount of growth as measured by the non-dialysable nitrogen content. Polysaccharide production, as measured by the polysaccharide: nitrogen ratio, was increased in all strains when growth was limited by a restricted supply of nitrogen source so that added carbohydrate remained in relative excess. A low incubation temperature, 15–20° instead of 35°, influenced polysaccharide production differently in the various strains and species; thus it greatly increased production in E. coli strains, but decreased it in A. cloacae strains grown on certain media. The various strains showed considerable differences in the amount of polysaccharide production and in the distribution of the polysaccharide between the different possible sites of accumulation: i.e. intracellular, capsular and as loose slime. The mucoid strains produced the largest amounts of polysaccharide, most of which was present extracellularly as capsules or slime; the smooth strains produced much smaller amounts, almost entirely intracellular; a rough strain produced least of all. The antigenic constitution of certain strains was examined, particularly that of a mucoid capsulate A. aerogenes and mucoid non-capsulate and non-mucoid smooth variants derived from it. The designation of such morphological and immunological variants is discussed.
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Transport of Phosphate across the Osmotic Barrier of Micrococcus pyogenes: Specificity and Kinetics
More LessSUMMARY: The system coupling inorganic phosphate exchange across the osmotic barrier of Micrococcus pyogenes var. aureus (Staphylococcus aureus) strain Duncan is highly specific for phosphate, probably for the H2PO′4 ion. Arsenate, however, can replace phosphate. The exchange is inhibited by thiol reactors, certain anions and certain uncouplers of oxidative phosphorylation. The specificity and kinetics of the exchange suggest that the phosphate is carried in the osmotic barrier as R-phosphate groups moved to and fro across the barrier by thermal agitation, the heat of activation for the movement being 37,400 cal. mole, of which at least 17,700 cal./mole is an entropy component. The exchange of the phosphate of the R-phosphate groups in the barrier with inorganic phosphate on either side may be enzymically catalysed, the free energy of the R-phosphate bond being conserved. Alternatively, the R-phosphate groups may dissociate or hydrolyse, forming free H2PO′4 ion and R, the latter then being unable to return across the barrier until R-phosphate is again formed by the spontaneous uptake of H2PO′4 ion.
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Studies of some Presumptive Lactobacilli isolated from the Rumens of Young Calves
More LessSUMMARY: Ten out of thirteen isolates of Gram-positive rods from the rumens of young calves proved to be catalase-negative and were further studied by methods suitable for lactobacilli. Four isolates from two calves, one of which was aureomycin-fed, proved to be Lactobacillus brevis Three isolates from a very young calf not fed aureomycin were provisionally identified as an anaerobic variant of L. lactis. The remaining three isolates obtained from an aureomycin-fed calf were all motile, homofermentative and mannitol-fermenting, and could not be identified with any known species of Lactobacillus; this organism produced a mixture of dextrorotatory and inactive lactic acid from glucose. The fermentation reactions of all the presumed lactobacilli isolated in this study were clear-cut and reproducible.
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A Selective Medium for the Primary Isolation of Haemophilus pertussis and Haemophilus parapertussis
More LessSUMMARY: A description is given of a selective medium which supports the growth of Haemophilus pertussis and Haemophilus parapertussis and largely inhibits the growth of Haemophilus influenzae. The medium contains horse-meat extract, horse blood, salt agar, 2 μg. 4:4′-diamidino-diphenylamine-dihydrochloride/ml. and 0·3 unit penicillin/nil. The medium is of value in the primary isolation of H. pertussis and H. parapertussis.
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Parasexual Recombination in Penicillium chrysogenum
More LessSUMMARY: Roper’s (1952) technique for the isolation in filamentous fungi of strains carrying in their hyphae diploid nuclei heterozygous for known markers has been applied with minor modifications to a third species: Penicillium chrysogenum. One of these modifications is the use of ‘dwarf’ (stunted growth) mutants for growing balanced heterokaryons. Heterozygous diploid strains of P. chrysogenum behave like those of the other two species in yielding, vegetatively, new strains with recombined properties. This behaviour can be marshalled for the deliberate breeding of improved industrial strains.
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The Behaviour of a Temperate Phage of Pseudomonas aeruginosa compared with that of a Serologically related, Virulent Mutant
More LessSUMMARY: A temperate phage of Pseudomonas aeruginosa (P. pyocyanea), on addition to a non-Iysogenic indicator strain of the organism, produced a lysogenic culture with a high spontaneous rate of free phage production. A virulent mutant, serologically related to the temperate phage, was obtained from this lysogenic culture; this mutant did not give rise to lysogenically infected bacteria. Both virulent and temperate phages, acting on an indicator strain, had latent periods of 90 min., and the multiplication of each was inhibited by a phenanthridine added immediately after adsorption. This indicated that the initial stage of infection is the same for both types of phage. The production of free phage (i.e. the prophage to phage change) by the lysogenic culture derived from the temperate phage was not inhibited by the drug.
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The Effect of Oxygen on the Growth and Metabolism of the Aerobic Thermophilic Actinomycete Micromonospora vulgaris
More LessSUMMARY: In the presence of pure oxygen at one atmosphere pressure Micromonospora vulgaris is unable to form in liquid media a surface pellicle of growth-bearing aerial mycelium. The production of bottom growth is either unaffected or stimulated by oxygen. Vegetative mycelium which develops from spores in Warburg vessels has an oxygen uptake that is similar in the presence of air or oxygen. Aerial mycelium, harvested from growths in air. shows marked differences as regards oxygen uptake in the presence of air or oxygen; oxygen is inhibitory. Some evidence is presented to show that the effect of oxygen may be connected with the inactivation of essential -SH groups of thiol enzymes.
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Factors affecting Production of Cellulose at the Air/ Liquid Interface of a Culture of Acetobacter xylinum
M. Schramm and S. HestrinSUMMARY: The cells in a developing culture of Acetobacter xylinum in a static liquid glucose medium were swept to the surface by the flotation of a submerged cellulose net. The net was probably pulled to the surface by adsorbed carbon dioxide given off by the metabolizing cells. The relatively high oxygen pressure at the aerated surface of a static liquid culture mediated the rapid production of cellulose in the surface layer. A. xylinum produced less cellulose in swirled than in static nutrient medium. Cellulose in the swirled medium occurred in the form of remarkable bodies, spherical, jointed or stellate in form, up to 10 mm. in size. The swirling favoured the overgrowth of the wild type organism by mutants which were specifically deficient in the ability to form cellulose. On the basis of the type of colonial growth and of the pellicle characteristics, two groups of A. xylinum mutants with an extreme deficiency in cellulose-forming ability and one with an intermediate degree of deficiency were differentiated.
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- Corrigendum
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