- Volume 51, Issue 3, 1968
Volume 51, Issue 3, 1968
- Articles
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The Relationships of Bacteria Within the Family Bacteroidaceae as shown by Numerical Taxonomy
More LessSUMMARY: A comparison, by numerical taxonomy methods, was made of 72 named or freshly isolated strains of Gram-negative anaerobes which were considered to belong within the family Bacteroidaceae. In the first analysis 57 strains were compared. Representative strains were then selected and compared with additional named strains in a second analysis. Four phena were identified: (1) strains of Sphaerophorus, Fusobacterium and Bacteraides melaninogenicus, (2) Bacteroides, (3) unnamed poultry isolates, (4) a second group of unnamed poultry isolates. The most useful differential tests were found to be: (a) cell morphology, (b) the terminal pH value in glucose broth and the production of formic, acetic, propionic or butyric acids, (c) the production of propionic acid from threonine, (d) growth stimulation by bile, (e) the effect of various inhibitors.
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The Influence of Certain Trace Metals on Bacterial Growth and Magnesium Utilization
More LessSUMMARY: The uptake of Mg2+ in Mg2+-limited cultures of the Gram-negative Escherichia coli is rapid and is complete some time before the onset of the stationary phase. In similar cultures of the Gram-positive Bacillus megaterium and B. subtilis F3 growth and Mg2+ assimilation cease at the same time and when only part of the available Mg2+ has been utilized; thereafter efflux of the cation may occur. In these cultures, as in dilute suspensions of the bacilli in a Mg2+-deficient medium, viability is maintained in a high percentage of the organisms, and growth occurs on the addition of Mg2+ even if this is delayed for 20 hr. The minimum growth-requirement for Mg2+ varies for different Gram-positive bacilli and is particularly low for Bacillus subtilis var. niger. The response of this organism to Mg2+ is unaffected by Mn2+. The Mg2+ requirements of B. megaterium and B. subtilis F3, however, are reduced by 25 μM Mn2+. Although this concentration of Mn2+ is unable to support growth of these bacilli in the complete absence of Mg2+, it appears to stimulate the uptake of the latter cation from dilute solutions. Mn2+ also is assimilated during growth by both Gram-positive and Gram-negative bacteria, although less efficiently than Mg2+, and is incorporated into the ribosomes.
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Formation and Structure of Extracellular Glucans Produced by Claviceps Species
More LessSUMMARY: Submerged cultures of Claviceps fusiformis (Loveless) became progressively viscous during the incubation because of the production of an extracellular polysaccharide. The polysaccharide was shown to be a branched glucan with a β1 → 3 linked main chain having single glucopyranosyl units at intervals along it in the β1 → 6 configuration. For most of the media investigated growth at 27° and between pH 5 and 6 was accompanied by glucan production, which ceased when growth was arrested by lack of nutrient. The glucan was re-metabolized by the fungus only to a limited extent as the culture aged; the degree of branching varied during the culture period. The unit amount of glucan synthesized was not affected by numerous successive subculturings over a period of several months, but the product from the later cultures had a greater degree of branching. Branched glucans of similar structure to the above were also detected in low concentration in the natural sclerotia. The presence of β1 → 3 linked glucans in the cell walls of this and other fungal strains examined was also indicated.
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A Microthread Technique for Studying the Viability of Microbes in a Simulated Airborne State
More LessSUMMARY: A technique is described in which airborne micro-organisms are captured on ultra-fine spider threads. In this state the organisms may be subjected to any environment of interest for extended periods of time, during which their loss of viability may be assayed. Experiments are described which show that the loss of viability is quantitatively similar to that in the true airborne state, provided that the microthread and aerosol environments are identical and that certain other precautions are observed.
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Cell Wall Composition of the Mycelial and Blastospore Forms of Candida albicans
More LessSUMMARY: Cell walls were obtained from the mycelial and blastospore forms of Candida albicans; these were delipidized and separated into alkali-soluble and alkali-insoluble fractions. The detailed composition of these fractions was determined in organisms grown on different media at 37° and on the same medium at different temperatures (blastospores 30°, mycelium 40°). The composition of the wall of each form was found to be constant, irrespective of growth conditions, except for some variation in the amounts of mannose and glucose in wall hydrolysates. The alkali-insoluble fraction from the mycelial form contained 3 times as much chitin as that from blastospores and only about one third as much protein. The protein from these two fractions showed marked differences in amino acid composition. Differences between the two morphological forms in the amounts of carbohydrate and protein in the alkali-soluble fractions were also found. The results are discussed in relation to other studies of cell-wall composition in the dimorphic
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Moraxella kingii sp.nov., a Haemolytic, Saccharolytic Species of the Genus Moraxella
More LessSUMMARY: A new Moraxella species, Moraxella kingii, is described. It is characterized by β-haemolysis, acid production from glucose and maltose, and lack of catalase activity. The strain 4177/66, isolated from a nose swab, is designated as the type strain.
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The Taxonomy of the Genera Moraxella and Neisseria
More LessSUMMARY: A reclassification of the Neisseriaceae is proposed, involving: (1) Inclusion of Moraxella as a genus of Neisseriaceae. (2) Transfer of Neisseria catarrhalis, N. ovis and N. caviae to Moraxella, or, alternatively, creation of a new genus for these species. (3) Unification of the species Neisseria flava, N. perflava and N. subflava under the name N. subflava. (4) Unification of the species Moraxella lacunata and M. liquefaciens under the name M. lacunata. (5) Exclusion of the genera Veillonella and Gemella from Neisseriaceae. The relationships of the organisms Acinetobacter anitratus and A. Iwoffi to the Neisseriaceae, if any, have not yet been sufficiently clarified to suggest the inclusion of these organisms in Neisseriaceae. Until this has been studied in more detail, the genus Acinetobacter appears to be suitable.
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Evolution of Developmental Stages in Cultures of Bacillus cereus
More LessSUMMARY: Cultures of Bacillus cereus grown in a chemically defined medium with glucose under standardized conditions followed a reproducible pattern of development giving good spore yields in less than 24 hr. Samples were withdrawn at intervals and individual organisms were classified into developmental states by four methods: (1) Gram reaction; (2) growth potential as revealed by the microcultures derived from single organisms or chains of organisms isolated into microdrops; (3) ability of individual organisms to take up neutral red; (4) electrophoretic distribution of organisms through a pH gradient. From the results we conclude that at most times the population was heterogeneous with respect to state of the organisms and that at least some of the shifts in state were quantal, in the sense that each state was relatively stable and that the transition from one state to the next rapid. There was a cyclical appearance and disappearance of organisms stainable with neutral red. Waves of stainable organisms were correlated with the break-up of chains into smaller units and with the lysis of a proportion of the organisms.
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Ultrastructural Changes During Germination of Ascospores of Neurospora tetrasperma
More LessSUMMARY: A technique is described for fixing and embedding dormant ascospores of Neurospora tetrasperma, whose impermeability has made them difficult subjects for electron microscopy. The ultrastructure of dormant and germinating spores has been compared. Endoplasmic reticulum occurs relatively infrequently in dormant ascospores whereas germinating ones have large amounts. An unusual structure, consisting of concentric membranes of varying degrees of complexity, appears after activation and disappears after extension of the germ tube. This membrane complex is continuous with the endoplasmic reticulum and may be its origin during germination. Mitochondria in dormant ascospores are larger and less numerous than in germinating ones. Two new elements of the ascospore wall are described, one of which may contribute to the relative impermeability of these forms. Nuclei increase in number during germination, but the exact number of divisions is not known.
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Levels of Resistance in ribosomes from Genetically Linked, Streptomycin-resistant Mutants of Pneumococcus
More LessSUMMARY: A streptomycin-sensitive strain and six streptomycin-resistant mutants of pneumococcus have been studied. These strains differed in resistance to streptomycin over a 5000-fold range, and the resistance mutations occurred at recombinationally distinct sites of a single genetic locus (the str locus.) The effects of streptomycin on cell-free amino acid incorporating systems prepared from each of the strains were studied. Both polyuridylic acid (polyU)- and endogenous mRNA-directed systems were employed. As in Escherichia coli, sensitivity to streptomycin was found to reside in the ribosomal fraction of the amino acid incorporating system.
Streptomycin caused both inhibition of 14C-phenylalanine incorporation and stimulation of 3H-isoleucine incorporation in poly U-directed experiments. The resistance of the amino acid incorporating systems to these effects of streptomycin paralleled the streptomycin resistance of the strain from which the system was derived. In endogenous mRNA-directed systems the incorporation of 14C-valine and 3H-isoleucine was followed simultaneously. Streptomycin caused an inhibition of valine incorporation and a lesser inhibition of isoleucine incorporation. At a higher magnesium concentration streptomycin caused a stimulation of isoleucine incorporation while still inhibiting valine incorporation. The disparate behaviour of isoleucine and valine incorporation in the presence of streptomycin may be due to streptomycin-induced misreading of endogenous mRNA. As in the poly U-directed experiments, the magnitude of the effects of streptomycin on endogenous mRNA directed amino acid incorporation correlated in an inverse fashion with the resistance of the strain from which the system was prepared.
These results lead us to conclude that the ribosome is the primary target for streptomycin in pneumococcus. We propose that the affinity of the ribosome for streptomycin at a critical site or sites determines the level of resistance of the bacterium, and that this affinity is affected by mutations in the str locus.
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The Effects of Various Anions and Cations on the Lysis of Yeast Protoplasts by Osmotic Shock
More LessSUMMARY: The lysis of yeast protoplasts as a function of the tonicity and composition of the suspension medium was examined. The resistance of the protoplasts to lysis by osmotic shock was lowered by certain chelating agents and at low pH values. The effects of chelating agents on the lysis of the protoplasts were inhibited by K+, Na+, Mg2+ and spermidine. Chelating agents increased lysis only when the protoplasts were undergoing osmotic stress, and the cations did not influence lysis unless chelating agents were also present. The presence on the protoplast membrane of a cation-binding site which is involved in maintaining the structure of the membrane is inferred.
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Metabolic Lysis of Yeast Protoplasts
More LessSUMMARY: Yeast protoplasts which were in osmotic equilibrium with a 0.55 M-mannitol solution underwent lysis when glucose was added to the suspension. Lysis was dependent on glucose metabolism and was accelerated when chelating agents were added to the medium. Lysis in the presence of glucose and chelating agents was inhibitied by alkali metal ions, magnesium, spermidine and by increasing the tonicity of the test medium. The inhibition of lysis by K+ and Na+ when chelating agents were present conformed to a Michaelis-Menten type relationship with apparent dissociation constants of 2–5 × 10–4 M and 3–6 × 10−3 M for K+ and Na+, respectively.
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The Isolation and Properties of the Yeast Cell Vacuole
More LessSUMMARY: When glucose and a chelating agent such as EDTA were added to yeast protoplasts suspended in 8.5% (w/v) mannitol solution at pH 6.4 almost all the protoplasts lysed and the main vacuole was released as a discrete structure from about 75% of the protoplasts. The isolated vacuoles were themselves sensitive to osmotic shock and exhibited vital-staining reactions. They are therefore considered to be relatively undamaged. Some of the properties of the isolated vacuoles are described.
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Polyphosphates of the Yeast Cell Vacuole
More LessSUMMARY: The distribution of phosphorus compounds in fractions isolated from metabolically lysed yeast protoplasts by centrifugation at 2000 g was examined. About 40% of the acid-soluble phosphorus compounds was associated with a particulate fraction which sedimented at 2000 g and which was rich in vacuoles. This phosphorus was present largely as polyphosphates of relatively high molecular weights. Evidence is presented to support the view that this polyphosphate fraction is contained in the vacuole sap. The phosphorus of the crude vacuole fraction was labelled only slowly when the protoplasts were allowed to take up 32P-orthophosphate. The phosphorus entering this fraction appeared to be derived from precursors present in the 2000 g supernatant fluid fraction.
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Metabolism of a Plant Wax Paraffin (n-Nonacosane) by a Soil Bacterium (Micrococcus cerificans)
More LessSUMMARY: Long-chain paraffins, such as nonacosane, reach the soil from plants and are degraded by micro-organisms. The ability of one soil organism, Micro-coccus cerificans, to grow on cabbage paraffin (n-nonacosane) was studied. Unlike the pattern seen with hexadecane, waxy esters were not produced when nonacosane was the sole carbon source, but esters were formed when a co-oxidation technique of [14C] n-nonacosane with hexadecane was employed. The alcohol and acid portions of the radioactive esters formed were primarily of chain length C16 C17 and C18; neither nonacosanol nor nonacosanoic acid were detected. Thus the nonacosanol and nonacosanoic acid which might have been produced from n-nonacosane must have been oxidized to shorter-chain compounds which in turn were incorporated into waxy esters as well as other lipids.
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