- Volume 32, Issue 3, 1963
Volume 32, Issue 3, 1963
- Article
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The Carotenoid Pigments of Mycoplasma
More LessSUMMARY: All the Mycoplasma organisms examined, which did not require a sterol as a nutrient, contained a carotenoid pigment identifiable as the hydrocarbon, neurosporene, and a carotenol. The carotenol occurred as the free alcohol, esterified with fatty acids, and in glycosidic linkage with glucose. The carotenyl glucoside in two organisms was hydrolysable with β-glucosidase, indicating the glucosidic linkage to be in the β configuration. The carotenoid compounds found in these organisms are analogous to the sterol compounds found in sterol-requiring organisms. Cholesterol supplied in the culture medium spared the synthesis of the carotenoids. Carotenols are postulated to serve in reactions which involve substrate transport and end-product transport across the cell membrane.
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Quantitative Aspects of the Protection of Freeze-Dried Escherichia coli Against the Toxic Effect of Oxygen
More LessSUMMARY: Various substances protect dry Escherichia coli against oxygen. The concentration of these substances in the bacterial suspension, necessary to achieve a given degree of protection, is a function of the concentration of the bacteria in the suspension. The protector seems to act in the dry state. The viability of freeze-dried bacteria, unexposed to oxygen, may also depend on the concentration of the bacterial suspension. A common mechanism is suggested to explain the dependence of killing on population density, both during freeze-drying and during exposure of dried organisms to oxygen. The viability of bacteria during freeze-drying and of dried bacteria exposed to oxygen are both markedly affected by the presence of certain substances such as serum albumin or Bacto-protone.
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The pH Value at the Surface of Bacillus subtilis
More LessSUMMARY: The reaction between penicillin and the penicillinase of Bacillus subtilis strain 749c, in the cell-bound and the free states, was studied over the range pH 3.9-9.0. The results suggested that the bound penicillinase behaved as though it were reacting in an environment of significantly lower pH value than that of the bulk phase. This effect was not as great as that calculated from electrokinetic data for B. subtilis surfaces. Various ways of interpreting the data are discussed.
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The Genetic Basis of Actidione Resistance in Neurospora
More LessSUMMARY: Seven actidione-resistant mutants recovered from separate strains of Neurospora crassa are due to mutations of single genes at either of two loci: act-1 (located between nit-1 and aur in linkage group I) and act-2 (located close to sp in linkage group V). Mutant alleles at both loci are dominant over their wild-type alleles in heterokaryons. Both genes are located in well marked chromosome arms, and scoring is distinct.
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An Analysis of the Vi-Phage Typing Scheme for Salmonella typhi
More LessSUMMARY: The seventy-two currently recognized Vi-phage types of Salmonella typhi have been examined in order to determine, where possible, their structural formulae. The genetic nature of the changes in host range of the corresponding typing adaptations of the Vi-phage II has also been investigated.
Thirty-seven temperate phages have been isolated from the type strains and type-determining ability has been demonstrated in all but five of these phages. Several of the determining phages were found in more than one type strain and it is probable that no more than 16 different determining phages are represented in our collection. Because there are fewer phage reactions to be eliminated in cultures already possessing a restricted sensitivity spectrum to the typing adaptations of Vi-phage II, some of the determining phages (‘semi-determining phages’) display their full effect only in such cultures.
One determining phage, d1-C, can co-operate with others, especially phages d8 and d9, in multiply lysogenized cultures to produce an effect which is more than a summation of the known type-determining powers of the individual phages concerned. Moreover, the type-determining effects of phages d1-C, d8, and d9 in singly or doubly lysogenized cultures are influenced by the temperature of incubation.
As has been shown by earlier workers, the changes in host-range of Vi-phage II that produce the Vi-typing phages may be phenotpic (host-induced) or genotypic (mutational) in nature, or a combination of these two types of variation. Amongst the current typing phages are represented eighteen different phenotypic modifications and forty-three different host-range mutants. Many of these mutations seem to be related to each other but their chromosomal distribution has not been mapped.
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The Use of Soft Agar in the Study of Conditions Affecting the Utilization of Fermentable Substrates by Lactic Acid Bacteria
More LessSUMMARY: Lactobacilli, streptococci, leuconostocs, pediococci and aerococci were examined in a soft agar medium which provided aerobic and anaerobic conditions in the one culture. The relation to oxygen varied in some instances with the energy source and the method by which it was sterilized. Other variations were determined by the temperature of incubation, the pH value of the medium and the salt concentration. Only a proportion of the organisms showed preferences or requirements for diminished aeration or anaerobic conditions. In some cases an aerobic environment was optimal or essential for the utilization of a fermentable substrate. The soft agar medium showed that the fermentation of sugars and other substances might occur as a sequel to mutation. Liquid media were compared with soft agar media; they provided little information about oxygen relationships. This comparison suggested several possible reasons for the variability of lactic acid bacteria reported by investigators who used liquid media in tests for fermentation.
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The Spore Surface in Pithomyces chartarum
More LessSUMMARY: Crystalline spicules of sporidesmolides, together with some lipid, form the surface layer of spores of Pithomyces chartarum. The formation of the spicules is controlled by the amino acids present in the culture medium.
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Fungi in the Air of Hospital Wards
More LessSUMMARY: The fungal flora of the air of hospital wards was investigated by using slit samplers. Isolations were made on Sabouraud glucose agar and particular attention was paid to the flora which grew at 37°. Aspergillus fumigatus was recovered on each of the 78 days of sampling and reached peak of incidence in the autumn and winter months; no other fungal species was recovered at 37° with such regularity. Bed sweeps revealed the presence of these fungi on blankets in the hospital wards. The mean equivalent diameter of the air-borne particles was determined for several fungal species and was found to correspond closely to that of individual spores. No dissemination of fungal particles by four patients with the hypersensitivity type of aspergillosis or by one patient with an aspergillus mycetoma was observed.
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A Systematic Study of the Genus Spirillum which Occurs in Oxidation Ponds, with a Description of a New Species
More LessSUMMARY: A systematic study of the spiral form bacterial flora of oxidation ponds has been made. Three known species, namely Spirillum itersonii, S. serpens and S. volutans, were constantly found. A primary enrichment medium for S. volutans from natural sources is given. A new species has been isolated; its main characters are: strictly aerobic, catalase-positive, does not grow under anaerobic conditions in the presence of nitrate, forms microcysts, differs in carbon-source utilization from previous described species. The species has been named Spirillum peregrinum.
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The Growth of Myxamoebae of the True Slime Mould, Didymium nigripes, in Axenic Culture
More LessSUMMARY: Myxamoebae of Didymium nigripes were grown in a peptone + yeast extract + glucose broth to which formalin-killed Aerobacter aerogenes or Bacillus megaterium had been added. Either the formalin-killed bacteria or a fraction from broken bacteria was indispensable for growth. The activity of the bacteria was destroyed by heat. The supernatant fluid of sonically disrupted bacteria supported growth; the active fraction of this was non-dialysable and was precipitated by ammonium sulphate. Lysed bacterial protoplasts did not support growth. Numerous compounds were tested unsuccessfully in attempting to eliminate the bacterial factor. When glucose was omitted from the medium the initialgrowth rate did not change but the population began to decrease rapidly after the fifth day.
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The Relation of Polyphenoloxidase in Leaf Extracts to the Instability of Cucumber Mosaic and Other Plant Viruses
More LessSUMMARY: Extracts made with buffered sodium diethyldithiocarbamate (DIECA) or potassium ethylxanthate from tobacco leaves infected with cucumber mosaic virus (CMV) were 5--500 times more infective than those made in buffer alone, or in buffer containing three other metal chelators which did not prevent the extracts going brown. DIECA preserved infectivity slightly better than did potassium ethylxanthate; both prevented browning equally. With DIECA in the extraction fluid, infectivity was not increased by other substances that enabled mitochondrial enzyme systems to be removed intact. CMV was inactivated by leaf polyphenols only when these were being oxidized. Oxidized polyphenols from virus-free leaves did not inactivate CMV when added together with copper, whereas deproteinized extracts of leaves crushed in an atmosphere of nitrogen did. When copper and chlorogenic acid, the main polyphenol in tobacco leaves, were added to infective extracts that contained polyphenoloxidase, the chlorogenic acid was oxidized and CMV was inactivated. A tobacco necrosis virus was slightly inactivated by incubating leaf extracts with chlorogenic acid and copper, but four other viruses were not. The tobacco necrosis virus was also the only one of these five to be at all stabilized by DIECA in the extraction fluid. The reported instability of some other plant viruses in leaf sap may mean that they also are susceptible to inactivation by polyphenoloxidase systems.
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Copper-dependent and Iron-dependent Inactivations of Cucumber Mosaic Virus by Polyphenols
More LessSUMMARY: Extracts made by crushing infected tobacco leaves in buffer solution containing sodium diethyldithiocarbamate (DIECA), centrifuging at 8000g, and dialysing the supernatant fluids against dilute buffer, were used to study the inactivation of cucumber mosaic virus (CMV). Incubating such extracts with chlorogenic acid and copper inactivated them; inactivation was usually much less when they were incubated with chlorogenic acid alone. Inactivation did not occur in vacuo or when DIECA was added. DIECA did not reactivate inactivated virus. CMV was inactivated rapidly by incubating with caffeic acid and copper, and slowly with catechol and copper, but not with five other phenols. The end-products of oxidation formed when chlorogenic acid was incubated with extracts of uninfected leaved did not inactivate CMV. Some features of the CMV-inactivating system are explained by the properties of tobacco leaf polyphenoloxidase. The compounds most effective in preserving the infectivity of CMV during extraction from leaves, DIECA and potassium ethylxanthate, are those which most strongly inhibit the enzyme. Conversely, the polyphenols that inactivate CMV in vitro are those oxidized most rapidly. Inconsistent effects of copper on the in vitro inactivating system can be partly explained by the different copper requirement of the polyphenoloxidase in extracts from plants infected for different times. Iron salts also accelerate the inactivation of CMV by chlorogenic acid. The process requires air and is prevented by DIECA; iron did not reactivate the DIECA-inhibited polyphenoloxidase. This system seems different from the one stimulated by copper. The concentration of iron in leaf extracts is usually less than that needed by the inactivating system.
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The Cellulolytic Activity of Pure Strains of Bacteria from the Rumen of Cattle
More LessSUMMARY: The in vitro breakdown of degraded and undegraded varieties of cellulose was examined by using pure strains of bacteria isolated from the rumen of cattle. One strain of Bacteroides succinogenes, two strains of Ruminococus albus and two strains of Ruminococcus flavefaciens were allowed to ferment ground cellulose power (prepared from filter paper), cellulose powder (Whatman) and undergraded cotton fibres, the extent of breakdown being followed by loss of weight of the insoluble substrate. All five organisms were highly active on degraded ground cellulose powder and dissolved 72--90%, but only one organism, B. succinogenes strain s-85, was equally effective on cellulose powder (Whatman) or on undergraded cotton fibres. R. flavefaciens strain FD-1 was somewhat less potent on the latter substrates, achieving 40 and 60% dissolution, respectively, of cellulose powder (Whatman) and cotton fibres. R. albus strain 7 and R. flavefaciens strain c-94 had negligible effects on cotton fibres (10 and 0% solubilization, respectively). R. albus strain D-89, producing 40% solubilization of cotton fibres, was intermediate in activity between R. albus strain 7 and R. flavefaciens strain FD-1. Cell-free preparations from culture filtrates of B. succinogenes strain s-85 gave only 4% breakdown of ground cellulose powder and up to 9% breakdown of cellulose powder (Whatman) in 17 days. Cell-free filtrates from the metabolism fluid of R. flavefaciens strain FD-1 or from the disintegrated organisms brought about 46 and 36% solubilization, respectively, of ground cellulose powder, but failed to attack cotton fibres. The results support the view that the capacity of an organism or cell-free enzyme to attack any one particular form of cellulose is no criterion of its ability to attack less degraded or undegraded types of cellulose.
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Thermopilic and Mesophilic Actinomycetes in Mouldy Hay
More LessSUMMARY: Actinomycetes isolated at 40° and/or 60° from mouldy hay included: Micromonospora vulgaris Waksman et al., Thermopolyspora polyspora Hens., T. glauca sp.nov., Streptomyces thermoviolaceus Hens., S. fradiae (Waksman et Curtis) Waksman et Henrici, S. griseoflavus (Krainsky) Waksman et Henrici, S. olivaceus (Waksman) Waksman et Curtis, and S. griseus (Krainsky) Waksman et Henrici.
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Characteristics of Marine Blue-green Algae with Uric Acid as Nitrogen Source
More LessSUMMARY: Two types of growth response were found with several species of marine blue-green algae when uric acid was sole nitrogen source for growth. For some species the cell type produced was typical of a blue-green alga and the growth rate was like that with other nitrogen sources. The second cell type was atypical in pigmentation. The organisms had a low nitrogen and ash content and the growth rate was much impaired. The cell type seen with uric acid is considered to be probably a minimum for sustained growth of a blue-green alga. Lipid accumulation was not a characteristic of the nitrogen-deficient condition, rather a carbohydrate reserve of a poly-glucose type is indicated. The growth data presented lead to the hypothesis that two different pathways for uric acid utilization may exist in blue-green algae, one probably a normal uricase type and the other a non-specific attack, possibly peroxidative.
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