- Volume 41, Issue 1, 1965
Volume 41, Issue 1, 1965
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THE SOCIETY FOR GENERAL MICROBIOLOGY
The Society for General Microbiology held its forty-second General Meeting at Queen Elizabeth College, Campden Hill Road, London, W. 8 on Thursday and Friday 7 and 8 January 1965. TL· following communications were made:
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- Article
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Interspecific Transformation in Azotobacter
More LessSUMMARY:This paper describes the results obtained in experiments on interspecific transformation in Azotobacter. When Azotobacter chroococcum was transformed with the DNA of A. vinelandii 6–10% of the colonies differed from the parent strain in colour, colony character and biochemical characteristics. Some of the transformant strains had higher nitrogen-fixing capacities than had the receptor strain. Transformants obtained by treatment of A. vinelandii with the DNA of A. chroococcum also had different colour, colony characteristics and capacity to grow in nutrient broth and peptone, but their nitrogen-fixing capacity was decreased.
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The Genetics of Bacillus licheniformis Penicillinase: a Preliminary Analysis from Studies on Mutation and Inter-strain and Intra-strain Transformations
More LessSUMMARY:A system of transformation in Bacillus licheniformis is described, in which a wide variety of markers can be transferred from one strain to another. A number of mutants affecting the regulatory, enzymie and serological aspects of penicillinase production are described, classified and discussed. A control gene for penicillinase synthesis was found to be linked to the structural gene in four wild-type strains of B. licheniformis. The electrophoretic properties of the penicillinases produced by the progeny of inter-strain crosses appeared to be affected by the type of cell in which the relevant structural gene was expressed.
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Utilization of Sodium Acetate by Shigella and Escherichia
More LessSUMMARY:The chemically defined medium with sodium acetate as sole carbon source (sodium acetate agar) devised by Trabulsi & Ewing (1962) was used to examine 414 strains of Shigella and 446 strains of Escherichia. None of the 414 Shigella cultures (belonging to the subgroups, A, B, C, D) utilized acetate and did not develop on sodium acetate agar, whereas about 95% of 283 anaerogenic and non-motile and all 163 aerogenic Escherichia isolates studied, utilized sodium acetate and grew on sodium acetate agar. It is concluded that the utilization of acetate on sodium acetate agar has a definite value for the differentiation of strains of the genera Shigella and Escherichia.
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The Morphology of Proteus Bacteriophages
More LessSUMMARY:The morphology of 28 bacteriophages active on members of the Proteus-Providence group of organisms was examined by a negative staining technique. Examples of the ‘T-even’, T3 and P22 morphologies were encountered as well as phages with non-contractile cross-striated tails resembling a group of coliphages. Others resemble staphylococcal and pseudomonas phages. Two phages (9, 7479) with octahedral capsids were encountered. A temperate Proteus mirabilis phage (12/57) and a temperate P. morganii phage (10041/2815) differ from phage P22 in that they possess collars. A P. rettgeri phage (7480 b) is unique in that it possesses a head with a regular hexagonal outline, a collar and a non-contractile tail while a Providence phage (9266) is believed to be the largest phage active on Gram-negative bacteria.
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RNA Metabolism of Rhodopseudomonas spheroides during Preferential Photopigment Synthesis
More LessSUMMARY:During anaerobic growth of Rhodopseudomonas spheroides the specific RNA content (μg. RNA/μg. protein) of cultures was directly proportional to the light intensity in which they were grown. Cultures subjected to a step-up in light intensity preferentially synthesized RNA until their specific RNA content increased to the value characteristic of growth at the higher light intensity. Conversely following a step-down in light intensity the rate of RNA synthesis fell below the rate of protein synthesis, and cellular RNA was diluted out to the value characteristic of growth at the lower light intensity. Adjustment of the differential rate of RNA synthesis in response to a change in light intensity was thus opposite to that of the differential rate of photopigment synthesis. Although a decrease in light intensity drastically decreased RNA synthesis some RNA continued to be formed. The RNA synthesized, like that in cultures maintained at a constant light intensity, consisted of soluble and ribosomal RNA and unstable RNA with sedimentation behaviour like m-RNA. Aerobic cultures of R. spheroides subjected to a marked decrease in O2 tension synthesized photopigments de novo without appreciably increasing their net content of RNA, but continued to synthesize small amounts of all the usual classes of RNA.
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Complementation of Non-flagellate Salmonella Mutants
More LessSUMMARY:Selection for resistance to phage χ led to the isolation from Salmonella typhimurium strain LT2 of fifteen non-flagellate (fla -) mutants due to spontaneous mutation at sites such that H 1 could be co-transduced with fla +. Treatment with phage P22 grown on LT2 fla + evoked swarms, i.e. motile (fla +) transductant clones, from all fifteen fla - mutants and from a fla - strain of S. paratyphi B; and also evoked trails, i.e. fla + abortive transductants, from all these mutants except four. When the fla - strains were crossed with each other by transduction all pairs yielded fla + clones, which indicated that none of the mutated sites was identical with, or overlapped, any other. In most pairs the appearance of trails showed that abortive transductants, of constitution fla1-fla2+/fla1+fla2- , were flagellate, as a result of complementation. The mutants fell into five groups, such that mutants of any one group complemented mutants of all other groups; these groups perhaps correspond to five fla genes. Some pairs of the ten strains of group A complemented, perhaps through intragenic complementation.
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Inheritance of the O Antigens of Salmonella Groups B and D
More LessSUMMARY:The inheritance of the O antigens of Salmonella was studied by Hfr x F- crosses of strains of groups B (antigens 4,5,12) and D (antigens 9,12). The partial antigens 4 and 9 behaved as if determined by allelic loci, in the sense that all recombinants had either antigen 4 or antigen 9; never both or neither of them. The O—4/9 locus thus defined was rather closely linked to his, the locus for histidine biosynthesis. The gene O—5 determining the presence or absence of partial antigen 5 (an O-acetyl group on a galactose unit) in group B was very probably introduced into a number of 9,12 recombinants. No antigen 5 appeared. The O—5 locus was also found to be linked to O—4/9 and his but the linkage was less close than that between O—4/9 and his. It is suggested that the loci O—4/9 and possibly O—5 are part of a large O-locus concerned with the synthesis of the specific side-chains of the somatic lipopolysaccharide, which perhaps includes the rou-B locus of Subbaiah & Stocker (1964).
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Effects of Nutrients on Self-Inhibition of Germination of Conidia of Glomerella cingulata
More LessSUMMARY:The percentage germination of suspensions of washed conidia of Glomerella cingulata decreased with increasing concentrations of the conidia in distilled water. With 30 conidia/mm.2 greater than 90% germination was obtained, whereas the conidia from the same batch gave less than 3% germination when there were 3000 conidia/mm.2. This inhibition of germination of crowded conidia was nullified by adequate amounts of peptone; but aeration by shaking had no influence, so that oxygen lack was ruled out as a factor in the inhibition. Various adsorbents, ion exchange resins, vitamins and germination stimulating chemicals were ineffective in inducing germination of crowded conidia. Czapek—Dox mineral solution, Hoagland's mineral solution and Czapek—Dox glucose solution gave respectively 10, 30 and 40% germination of crowded conidia. The germination of conidia was improved by repeated washing with distilled water. Addition of various mineral salts and trace elements (Mg, Fe, Mn, Bo, Zn, Mo, Cu) were relatively ineffective or toxic. Glucose, or mannitol did not induce germination. Peptone and phenylalanine were most effective in promoting the germination of crowded conidia, but only in massive doses. Bimodal response of germination of conidia to added nutrients was noticed. Since the conidia germinated, when present at low concentrations in redistilled water without added nutrients, the conidia could not be considered as nutritionally deficient. The beneficial effect of nutrients in promoting the germination of crowded conidia may be due to inactivation of inhibitory metabolites from the conidia.
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Differentiation of Porcine Mycoplasma Strains
More LessSUMMARY:Porcine Mycoplasma strains, previously called ‘swine enzootic pneumonia strains’ are antigenically closely related to Mycoplasma hyorhinis. Other porcine Mycoplasma strains which are culturally and antigenically distinct from M. hyorhinis are more heterogeneous and fall into four serotypes. M. granularum, however, is antigenically unrealted to these strains.
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DNA Base Composition, Flagellation and Taxonomy of the Genus Rhizobium
More LessSUMMARY:There is a correlation between the base composition of pure DNA from 35 strains of Rhizobium and their type of flagellation. There are two groups of Rhizobia. The peritrichously flagellated organisms, which usually grow fast, have a low % (guanine + cytosine) composition in the range 58·6–63·1%; these organisms occur in all cross-inoculation groups investigated. From a comparison with literature data it appears that this group is constituted by two subgroups: Rhizobium leguminosarum and R. meliloti. The subpolarly flagellated, slow-growing strains have a some-what higher (guanine + cytosine) content, mostly in the range 62·8–65·5%; these organisms appear to be specialized mainly for the lupin, soybean, cowpea, Lotus, Wistaria and Robinia groups, It is proposed that only one genetic species is involved, to be called Rhizobium japonicum. The rhizobia would thus contain only three genetic species. The relationship between the high and low (guanine + cytosine) groups is stressed by their closely related % (G + C) values, the near-identity of the average compositional distribution of the DNA molecules and because the peritrichous organisms not infrequently show a subpolar flagellum.
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Chromosome Behaviour at Meiosis in Saccharomyces cerevisiae
More LessSUMMARY:The behaviour of the chromosomes of diploid strains of Saccharomyces cerevisiae was studied in organisms which had been treated with snail digestive juice after fixation, and then stained with the HCl—Giemsa stain. Coagulation of chromatin was observed after late prophase-I in some strains and for this reason the chromosome number of these strains could not be determined. One diploid strain (H 102 x H 9) showed no chromatin coagulation, and was shown to have eighteen bivalents at metaphase-I.
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Metal-Complexing Agents as Metal Buffers in Media for the Growth of Aspergillus niger
More LessSUMMARY:The influence of metal-complexing agents on the mycelial growth rate, conidial germination and morphology of Aspergillus niger in shake-flask cultures was studied. The agents tested were: ethylenediaminetetra-acetic acid (EDTA), diaminocyclohexane-N,N-tetra-acetic acid (CDTA), diethylenetriaminepenta-acetic acid (DTPA), and nitrilotriacetic acid (NTA), which form soluble complexes, and ferrocyanide, which forms insoluble complexes. The agents were added singly to culture media in concentrations up to 9·4 mM. The sum of the concentrations of the complex-forming metals (Fe, Cu, Zn and Mg) added to the medium was 1·04 mM. At pH 6·5 mycelial growth rate was almost unaffected by any of the agents when they were added after the germination of conidia. At pH 3·5 ferrocyanide at 84 μM increased the mycelial doubling time by 30%, but the other agents had little effect on the mycelial growth rate at pH 3·5. EDTA, CDTA and DTPA at 1·04 mM inhibited germination of conidia at pH 6·5; lowering the pH partially relieved this inhibition. Ferrocyanide at 9·4 mM was without effect on germination at pH 6·5, but at pH 3·5 it strongly inhibited germination at 84 μM. The morphology of the organism was markedly affected by EDTA, CDTA, DTPA and ferrocyanide but not by NTA. In cultures without complexing agents or with NTA the organism grew in the form of large pellets with a filamentous periphery; such pellets formed a gelatinous conglomerate in the culture. With either EDTA, CDTA or DTPA at 1·04 mM or ferrocyanide at 84 μM, the organism grew in the form of small pellets with a smooth exterior; such pellets remained discrete and dispersed in the medium. These physiological effects are attributed to changes in the metal ion concentrations in the medium brought about by the complexing agents.
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The Effect of Calcium Nutrition on the Production of Diffusible Antigens by Rhizobium trifolii
More LessSUMMARY:Rhizobium trifolii grown in a defined medium deficient in calcium yielded additional diffusible antigens as compared with organisms receiving calcium or strontium. The two kinds of organisms were indistinguishable in respect of their somatic agglutinogens. The same additional precipitinogens were released from Ca-adequate bacteria by mechanical disintegration, freezing, drying, lysozyme or chloroform. Their occurrence in the untreated Ca-deficient bacteria is attributed to autolysis of these more fragile bacteria. The precipitinogen (‘a’ band) that was common to the Ca-adequate and Ca-deficient bacteria was not shared by a second strain of R. trifolii nor by 2 strains of R. meliloti. This ‘a’ antigen was heat stable and appeared to be a component of the cell wall, from which it could be separated in diffusible form by formamide extraction of whole bacteria, trypsin digestion of broken bacteria and by mechanical disintegration of prepared cell walls. Neither of the additional antigens (‘b’, ‘c’) was related to agglutination; both were found in Ca-deficient or mechanically broken bacteria of the other strain of R. trifolii; ‘c’ only was similarly shared with R. meliloti. The ‘b’ band antigen appeared to be an intracellular component and was heat labile. Like ‘a’, ‘c’ was heat stable and associated with cell wall, but evidently was not ordinarily exposed, although readily released by lysis or mechanical breakage. The extracellular polysaccharide was neither antigenic nor haptenic, but the preparation obtained from Ca-deficient and mechanically broken Ca-adequate organisms was persistently associated with a co-precipitating antigenic component (chiefly ‘a’ band).
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An Induced Enzyme in X-irradiated Escherichia coli: Comparison with Lethal Effects
More LessSUMMARY:The effect of X-rays on the synthesis of induced β-D-galactosidase was examined with Escherichia coli strain B and three of its mutants, i.e. the sensitive strain BS and two resistant strains B/r and B/H. With the parent strain E. coli B the extent of radiation-induced lethal damage depended on conditions of culture after irradiation, whereas radiation-induced inhibition of β-D-galactosidase was unaffected by the composition of the culture medium. The sensitivity of radiation damage to induction of β-D-galactosidase was about the same for E. coli strains B, B/r and B/H, the dose required to give 37% survival being 42 ± 6 krad; in E. coli BS the sensitivity to radiation was three times as great. Enzyme induction was one-half to one-third as radiosensitive as viability for the strains B/r, B/H and BS but with strain B it was one-tenth as sensitive when Oxoid Nutrient Medium was used. Oxygen enhancement ratios for lethal effects were always smaller than those for inhibition of enzyme synthesis.
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Nutritional Factors in Relation to Growth and Fat Synthesis in Mortierella vinacea
More LessSUMMARY:Growth and fat synthesis in Mortierella vinacea are influenced by a number of nutritional factors. Monosaccharide carbohydrates provided the best carbon source for growth and fat synthesis. Organic nitrogen substrates were inferior to ammonium phosphate for fat accumulation, although high yields of mycelium were obtained. These media probably enhanced protein synthesis. The balance between carbon and nitrogen in the culture medium influenced the rate at which fat synthesis occurred. High concentrations of carbohydrate (glucose) resulted in large yields of mycelium with a high fat content.
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Isolation of Variant Strains from Foot-and-Mouth Disease Virus Propagated in Cell Cultures Containing Antiviral Sera
More LessSUMMARY:Three strains of foot-and-mouth disease virus of type SAT 1 were propagated serially in cultures of pig kidney cells in the presence of gradually increased concentrations of specific antiserum. All showed an increase in their ability to multiply in the presence of the serum. With two of the strains, complement-fixation tests revealed that propagation under these conditions was associated with modification of antigenic structure, but antigenic differences were detected later than changes in the ability of all strains to multiply in the presence of antiserum. Processes of this nature may possibly result in vivo from similar interactions of virus and antibody in host populations.
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Effect of Dilution Rate and Growth-Limiting Substrate on the Metabolic Activity of Torula utilis Cultures
More LessSUMMARY:Torula utilis was grown in a chemostat, at several dilution rates, in media containing growth-limiting concentrations of glucose, xylose and ethanol; it was similarly grown in an NH4 +-limited medium (carbon source, glucose). The ‘steady state’ rates of oxygen uptake of cultures, and Q O2 values for washed suspensions of organisms separated from the cultures and incubated with each substrate, were determined at each dilution rate. Differences in oxidation rates indicated quantitative changes in the ‘constitutive’ enzyme content of organisms, which varied according to the growth rate and/or the nature of the growth-limiting substrate. The significance of these changes in terms of metabolic regulation and economy of enzyme synthesis is discussed.
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