- Volume 26, Issue 2, 1961
Volume 26, Issue 2, 1961
- Article
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Utilization of l-Glutamic and 2-Oxoglutaric Acid as Sole Sources of Carbon by Escherichia coli
More LessSUMMARY: A wild-type strain of Escherichia coli (W) did not utilize glutamate or oxoglu-tarate as sole source of carbon for growth, but mutants able to grow on each of these compounds were isolated. The abilities to utilize glutamate and oxoglutarate did not necessarily accompany each other. The evidence presented supports the view-that both kinds of mutant involve changes in a permeation mechanism. The mutation to growth on glutamate was always accompanied by appearance of sensitivity to inhibition by 2-methyl-dl-glutamic acid and by partial or even complete loss of glutamic acid decarboxylase. It is proposed that the permeation mechanism for glutamate also allows entry of 2-methylglutamate, a compound which prevents glutamine formation. The loss of glutamate decarboxylase remains unexplained.
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The Cultural and Physiological Characters of the Pediococci
More LessSUMMARY: The cultural and physiological characters of 89 strains of pediococci have been studied. Proposals are made for extension of the genus and its subdivision into two and possibly three groups. The reactions of eleven strains of Aerococcus viridans were also investigated.
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Serological Characters of the Pediococci
More LessSUMMARY: Rabbit antisera were prepared against 12 pediococcus isolates and tested by precipitin, precipitin-absorption and agglutination tests. Common precipitins for the three species Pediococcus cerevisiae, P. parvulus n.sp. and P. damnosus were demonstrated. An antiserum prepared against Aerococcus viridans (NCTC 7599) reacted with extracts of the homologous strain and 7 out of 10 heterologous Aerococcus viridans.
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The Production of Sporidesmin and Sporidesmolides by
More LessSUMMARY: Methods for the assay of sporidesmin and the sporidesmolides were worked out and used in the study of the production of these metabolites by Pithomyces chartarum (Commonwealth Mycological Institute, Kew, England, Herbarium no. 74473) growing on an enriched potato carrot medium. High yields of sporidesmin and the sporidesmolides were associated with high utilization of medium constituents. No increase in the quantity of sporidesmin isolated from unit volume of medium was observed after the third day of incubation, despite further rapid growth of the fungus; by contrast good correlation was observed between the weight of sporidesmolides produced and fungal growth. These results were successfully applied to the production of experimental quantities of these materials.
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Growth of Leptospira in Defined Media
H. Vogel and S. H. HutnerSUMMARY: Serum-free chemically defined media were developed for cultivating several Leptospira strains. Leptospira canicola, Ruebeusch strain, was the main test strain. Esterified fatty acids (monoolein, monostearin, methyl palmitate, methyl oleate) replaced serum. Fe++ over a narrow range replaced haemin. Thiamine was essential. Other vitamins added to thiamine-containing medium (nicotinic acid, pantothenate, putrescine, p-hydroxybenzoic acid, vitamin B12) speeded or increased final growth. Acetate stimulated growth moderately. Ammonium sulphate was favourable over a wide concentration range.
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Distribution of Urease in Clostridium perfringens Types
More LessSUMMARY: About five hundred strains of Clostridium perfringens were tested for ability to produce urease. There was found to be a distinct, although not complete, correlation between urease production and antigenic type. In types B and D there was also some degree of correlation between the production of urease and of λ-antigen. The distribution of urease between the six antigenic types of C. perfringens was not sufficiently sharp to be of use in type differentiation.
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The Measurement of the Liberation of Penicillinase from Bacillus subtilis
More LessSUMMARY: The formation of penicillinase, induced in a growing culture of Bacillus subtilis 6346 by a single addition of benzylpenicillin, spontaneously ceases after about 3 hr. The enzyme continues, however, to be released into the medium, thus permitting the process of its liberation to be studied independently from its production. By using the escape into the medium of a normally intracellular, maltose-inducible α-glucosidase as a more sensitive indicator of cell damage than direct measurement of lysis, it was concluded that at least 40 % of the penicillinase is liberated from the cells without gross disorganization of their structure.
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The Location of Cell-bound Penicillinase in Bacillus subtilis
More LessSUMMARY: Before penicillinase is released from a penicillin-induced culture of Bacillus subtilis it accumulates and up to 85% is found to be bound to the cells. This cell-bound penicillinase is not free in the cytoplasm since it cannot be released in a soluble state simply by rupture of the cell envelope. It appears to be attached to the cell in a fairly superficial location since up to 40 % is accessible to antiserum and up to 98 % can be released, by trypsin in the presence of hypertonic sucrose, from apparently intact cells.
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The Mechanism of Liberation of Penicillinase from Bacillus subtilis
More LessSUMMARY: The effects of various factors on the release of penicillinase from apparently undamaged cells of a growing culture of Bacillus subtilis were investigated. The enzyme was not eluted from the cells by treating them with high concentrations of salt. Its liberation did not take place at all at 0°, and was nearly completely inhibited at pH values below 6.0, whereas chloramphenicol, at concentrations sufficient to cause complete cessation of growth, caused only partial inhibition of enzyme release. The penicillinase-releasing action of extracts containing heat-labile ‘autolytic’ factors from older cells of the same organism could not be dissociated from their damaging effect on the cell, as indicated by concomitant release of the normally intracellular α-glucosidase. It is concluded that normal penicillinase liberation is controlled by enzymic reactions, as yet unidentified, involving detachment of the enzyme from structures superficially located in the cell envelope.
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The Genetic Relationship and Phenotypic Expression of Mutations Endowing Pneumococcus with Resistance to Erythromycin
More LessSUMMARY: Five spontaneous erythromycin resistance mutations arising independently in a pneumococcal strain have been studied. Three distinct levels of resistance are represented by these mutants (0.1, 1.0, and 10.0 μg. erythromycin per ml.). The mutations conferring resistance can be transferred to the sensitive parental strain through transforming DNA preparations. The transfer is discrete, in that the full level of resistance of the donor strain is always conferred upon the recipient. The length of time required for phenotypic expression of a mutation acquired by transformation depends on the particular marker.
A mutation in a given strain may either be replaced by or combine with a different mutation transferred from a donor DNA preparation. In the case of combination, the DNA of the recombinant is capable of transferring each of the mutations as well as the entire complex of mutations possessed by the recombinant. The frequency of transfer of the complex demonstrates the degree of linkage of the separable mutations. A group of mutations in a given recombinant strain may either display antagonistic, synergistic or non-synergistic effects on the phenotype.
Reverse mutations towards erythromycin-sensitivity generally involve alteration at the originally mutated sites, or at very closely linked sites.
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Transforming Activities and Base Contents of Deoxyribo-nucleate Preparations from Various Neisseriae
More LessSUMMARY: Genetic transformation was investigated among Neisseria spp. whose normal habitat is the nasopharynx of humans. Seven species, as characterized in Bergey's Manual (1957), were represented. Deoxyribonucleate (DNA) preparations from streptomycin-resistant mutants of N. meningitidis, N. perflava, N. flava, N. subflava, N. sicca, and N. flavescens conferred resistance upon streptomycin-susceptible parent strains of the corresponding species (intraspecific transformation) and of each other species (interspecific transformation). Ratios of interspecific to intraspecific transformation were 0.01 or higher for all possible combinations of DNA and recipient cells of the six species. On the other hand, N. catarrhalis cells, which exhibited high frequencies of intraspecific transformation, were not transformed at detectable frequencies by DNA from any of the six Neisseria species listed above. In turn, DNA from N. catarrhalis had little or no transforming activity for these other neisseriae.
Possible evidence of structural differences between these DNA's was sought by analysing the base contents of transforming preparations. The bases adenine, thymine, guanine and cytosine were present in about equal proportions in the DNA's of the six Neisseria: meningitidis, perflava, flava, subflava, sicca and flavescens. In DNA preparations from two strains of N. catarrhalis, however, adenine and thymine predominated. The ratio (adenine + thymine/guanine + cytosine) was higher than 1.4 compared to 1.0 for the others.
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The Role of Magnesium Ions in the Growth of Salmonella Phage Anti-R
More LessSUMMARY: Magnesium or certain other divalent metal ions are needed for the adsorption of phage anti-R to its host, a ‘rough’ strain of Salmonella typhi. In medium containing magnesium ions the infected organisms burst after a latent period of about 20 min. at 37° but when infected organisms are diluted into medium without added divalent metal ions phage growth is considerably inhibited. A rapid increase in phage titre occurs when magnesium ions are added late, i.e. at some time after the end of the normal latent period, to dilute cultures of phage-infected organisms. During the interval between infection and this late addition of magnesium ions no appreciable numbers of infective intracellular phage were detected after ultrasonic disruption of the organisms. It is concluded that in addition to being an adsorption cofactor, magnesium functions at some late stage in phage development. Phage anti-R is probably related to ϕX 174; it consists of particles approximately 30 mμ in diameter and the intact phage reacts similarly with formaldehyde.
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Electron Microscope Observations on the Surface Structures of Streptomyces violaceoruber
More LessSUMMARY: The surface structures of Streptomyces violaceoruber were studied by electron microscopy of intact organisms, carbon replicas and preparations of walls from disrupted organisms. A surface layer with a fibrillar structure was observed on the aerial hyphae and spores in all three types of preparation. The fate of this layer during spore formation and germination was studied; it is a loose covering which breaks when the spores separate and when the germ tubes emerge, and it is easily lost when the organisms are disrupted. No organized surface structures were observed on the underlying hyphal or spore walls.
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A Study of Two Marine Agar-Decomposing, Facultatively Anaerobic Myxobacteria
More LessSUMMARY: Two facultatively anaerobic agar-decomposing myxobacteria were isolated from marine mud and described as Cytophaga fermentans Bachmann var. agarovorans var. nov. and C. salmonicolor var. agarovorans var. nov. A third organism which does not attack agar was isolated from the same source; it has been included in the present study for comparative purposes. The specific name Cytophaga salmonicolor has been given to this organism. All organisms are characterized by exhibiting flexing and gliding motility and by absence of microcysts and fruiting bodies. The organisms can be grown in a mineral glucose medium, although growth is accelerated and more abundant when a vitamin mixture is included in the medium. CO2 is an absolute requirement for growth. Growth of C. fermentans var. agarovorans and C. salmonicolor var. agarovorans on aerobic plate cultures is markedly inhibited by 0.1 % glucose or galactose. Acetic, propionic and succinic acids are major end products of sugar fermentation of all three types. C. salmonicolor and C. salmonicolor var. agarovorans form in addition CO2 and H2, and small amounts of lactic and formic acids and ethanol.
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Atmospheric Content of Nigrospora Spores in Jamaican Banana Plantations
More LessSUMMARY: The air in three Jamaican banana plantations was sampled from 20 July 1960 to 15 April 1961 with a Hirst spore trap. Spores of Nigrospora were regular components of the air-spora. They exhibited a regular and sharply defined diurnal periodicity, rapid liberation of spores starting at about 07.00 hr. and reaching a peak between 08.00 and 10.00 hr.; very few spores were trapped during the night. This is consistent with the fact that spore discharge occurs only under conditions of decreasing vapour pressure. Rainfall and under-tree irrigation usually resulted in an appreciable increase in atmospheric content of Nigrospora spores. These high concentrations were maintained for 2-4 days before decreasing to characteristically low dry weather values. The highest daily mean concentration recorded was 1350 spores/m.3, an estimate of c. 14,000/m.3 being obtained at 08.00 hr. on the same day.
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Nodule Bacteria Associated with the Indigenous Leguminosae of South-Western Australia
More LessSUMMARY: Root-nodule bacteria (rhizobia) isolated in pure culture from legumes indigenous to south-western Australia were examined for cultural and infective characters. All isolated strains had cultural characters consistent with the slow-growing bacteria of the lupin or soybean type. None of the strains nodulated peas, clover or medic, but hosts from the other four recognized cross-inoculation groups were nodulated. Lupinus digitatus, Glycine hispida, Vigna sinensis and Phaseolus vulgaris formed a natural grouping on the basis of susceptibility to nodulation by the native strains. Within the narrower host range of the genus Lupinus it was found that L. digitatus, L. albus and L. pilosus grouped together on susceptibility to nodulation. whereas L. luteus, L. angustifolius and Ornithopus sativus were not nodulated by any of the sample strains. The use of this geographically isolated sample of rhizobia has further demonstrated the weakness of the present scheme of classification of the nodule bacteria, which is based on the infective character of the bacteria. A taxonomic system based on Adansonian principles could be applied to the classification of the rhizobia, and a procedure for attempting this is outlined.
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