- Volume 97, Issue 1, 1976

SUMMARY: The role of protein, RNA and DNA synthesis in the repair of thermal injury in Salmonella typhimurium was investigated. Thermal injury was assessed by the ‘minimal medium recovery’ system: after heat treatment, higher viable counts are obtained on minimal-medium agar than on complex-medium agar, and the ability of heated bacteria to form colonies on complex-medium agar is recovered when they are incubated in liquid minimal medium. This recovery is inhibited by rifampin and chloramphenicol, but not by nalidixic acid. In addition, rifampin causes a loss in viability. Alkaline sedimentation analyses of radioactively labelled DNA showed that hydroxyurea and rifampin, unlike chloramphenicol and nalidixic acid, cause DNA breaks in heated bacteria. The results indicate that rifampin is lethal to heated bacteria and that chloramphenicol, though not lethal, prevents repair of thermal damage.

SUMMARY: The principal products of endogenous metabolism of the obligate anaerobe Peptococcus prévotii were carbon dioxide, ammonia, acetate and butyrate, which are also produced by fermentation of nucleosides, purines and ribose, thus supporting our previous finding that RNA is the only cellular component to undergo substantial degradation under starvation conditions. Minor products were hydrogen, formate and propionate. The stoicheiometries of fermentation of xanthine, adenine, adenosine and ribose were determined. The ability to ferment exogenous nucleosides, purines and ribose declined rapidly on starvation, as did the ability to generate ATP from xanthine, and was paralleled by the loss of viability. However, addition of pulses of xanthine or adenine to organisms in the early stages of starvation sustained their adenylate energy charge and prolonged their viability. Evidence suggests that P. prévotii dies when its principal energy source (RNA) is depleted, and a possible explanation is that the transport function of the cytoplasmic membrane decays rapidly under these conditions so that, on transfer to a recovery medium, uptake of nutrients is inadequate to support growth.

SUMMARY: An examination of the soluble carbohydrates of the wheat stem rust fungus, Puccinia graminis Pers. f. sp. tritici Erikss. & E. Henn., showed the presence of glucitol (sorbitol), ribitol, fructose, and traces of xylitol, as well as confirming the presence of mannitol, arabitol, trehalose, inositol and erythritol. Ribitol and glucitol were major components in glucose-grown mycelium, and appeared to be the major components in mycelium parasitic on wheat leaves, but not in germinated or ungerminated uredospores. It is suggested that glucitol and ribitol may be intermediates (or by-products) of glucose utilization, whereas mannitol, arabitol and trehalose represent storage carbohydrates.

SUMMARY: The growth responses of an acetate-utilizing isolate of Butyrivibrio fibrisolvens to CO2, acetate and pyruvate were determined using a chemically-defined medium. Carbon dioxide was essential for growth and both acetate and pyruvate increased growth. 14C from [1-14C]acetate was found mainly in butyrate while 14C from 14CO2 or [1-14C]pyruvate appeared predominantly in formate and lactate. These results, together with those obtained with enzyme preparations, indicated pyruvate synthase, pyruvate-CO2 exchange and pyruvate formate lyase to be active.

SUMMARY: Gonococci (strain BS3) passaged three times and harvested directly from plastic chambers implanted subcutaneously in guinea pigs were compared with the parent strain (BS) grown in vitro. The strain grown in vivo produced smaller colonies than that grown in vitro and when examined directly in chamber fluid was sometimes not pilated. It was more resistant to the bactericidal action of human serum and more infective for guinea-pig chambers. In gel diffusion, extracts of the organisms adapted in vivo and cultured once on agar appeared to contain one or two antigens that were different from those in extracts of the in vitro grown organisms; and on polyacrylamide gels, electrophoresis of similar extracts showed one or more protein components for strain BS3 which were not seen for strain BS. Gonococci grown in guinea-pig subcutaneous chambers appear to be suitable for studies on the determinants of gonococcal pathogenicity.

SUMMARY: The bacterial drug-resistance plasmids Sa, R388 and R7K that comprise the W compatibility group were transferred by conjugation to species in the genera Escherichia, Salmonella, Shigella and Pseudomonas, chosen for their lack of common pili. On receiving the W plasmids, all strains produced pili, which were similar morphologically, at average frequencies of up to 3·0 pili/cell. The pili determined by the W plasmids were also related serologically, but unrelated to those of other plasmids. R− segregant strains which had lost their plasmids showed a simultaneous loss of both pili and drug-resistance characteristics.

W-pili are pointed flexible filaments 10 to 12 nm thick, with an average length of 450 nm. The best host found was Salmonella typhimurium.

SUMMARY: The linkage of two mutations leading to increased sensitivity to ultraviolet light and 60Co gamma rays was determined in the slime mould Dictyostelium discoideum using a genetic analysis based on the parasexual cycle. Diploids were selected from a mixture of radiation-sensitive, temperature-resistant and radiation-resistant, temperature-sensitive haploids on the basis of simultaneous radiation and temperature resistance. Analysis of drug-resistant haploid segregants of the heterozygous diploids indicated that one of the radiation-sensitive mutations, radA20, was linked to linkage group 1 whereas the other, radB13, was linked to the recently defined linkage group VI.

SUMMARY: Pigmentation mutants of Pseudomonas phenazinium unable to synthesize iodinin, or producing it only in reduced amounts, were isolated. The abilities of the mutants to synthesize nine other phenazines were also altered. Cross-feeding experiments and the altered patterns of pigment production suggested metabolic relationships between the phenazine pigments, and a scheme for their biosynthesis is proposed.

SUMMARY: The aspartase (l-aspartate ammonia-lyase, EC. 4.3.1.1) structural gene, aspA, was mapped by two-factor and three-factor transductional crosses using phage P1. Cotransduction frequencies between aspA and other markers were: ampA (69%); frdA (48 to 67%); mel (35%); purA (17%); fdp (1·6%). The sequence of markers within the corresponding segment (91 to 95 min) of the Escherichia coli linkage map was shown to be mel-aspA-ampA-frdA-purA-fdp.

SUMMARY: The temperature limits of growth of three psychrophilic yeasts, Leucosporidium frigidum, L. gelidum and L. nivalis, were examined. All species grew well at subzero temperatures (−1 °C). The maximum temperature of growth was significantly higher with glucose as substrate (18 to 20 °C) than with ethanol (17 to 18 °C). There was a positive correlation between the growth temperature and the degree of fatty-acid unsaturation of the cell lipids; the lower the temperature, the greater the degree of fatty-acid unsaturation. At subzero temperatures (−1 °C) with ethanol as substrate, 90% of the total fatty acid was unsaturated with linolenic (35 to 50%) and linoleic (25 to 30%) acids predominating. At temperatures close to the maximum for growth, linolenic acid accounted for less than 20% of the total fatty acid and oleic (20 to 40%) and linoleic (30 to 50%) acids were the major components. Difference spectra of intact cells showed marked changes in the ratios and amounts of individual cytochromes as a function of growth temperature. In L. frigidum with glucose as substrate, the ratios of cytochromes a+a 3:b:c at 8 and 19 C were 1:1·1:2·9 and 1:2·3:16·7 respectively. Similar changes in cytochrome ratios were noted for L. gelidum, but changes were much less marked for L. nivalis. The temperature effects were interpreted as supporting the view that membrane structure and composition are fundamental to temperature adaptation in psychrophilic yeasts.

SUMMARY: Cysts of Polytomella parva and Polytomella caeca were recovered after 7 days storage at cryogenic temperatures following drying on shredded filter paper, silica gel or without added substrate. Accelerated storage testing, by exposing dried material to elevated temperatures, indicated that shredded filter paper was the best of the substrates tested. Polytomella parva was recovered after 5 years storage at − 30 °C when dried on filter paper but not when dried on silic agel. Determinations of the number of cysts recovered indicated that viable cysts survived all conditions of storage tested. However, excystment following storage was delayed, the extent depending on storage conditions and the substrate used for drying. Most rapid recovery occurred when cysts were rehydrated immediately after drying, and after storage on filter paper at below − 70 °C.

SUMMARY: A new marine strain of the Planctomyces-Blastocaulis group of stalked, budding bacteria was isolated: the name Planctomyces maris is proposed. Cells were spherical to ovoid, exhibited longitudinal symmetry and had a single fibrillar appendage located at one pole of mature cells. Reproduction occurred by budding at the opposite pole of the cell. The resulting daughter cell was motile by a single subpolar flagellum. The organism was an obligately aerobic, mesophilic heterotroph which utilized 15 of 81 carbon sources tested for growth. It grew slowly, the shortest doubling time recorded being 13 h at 30 C. The DNA base composition was 505 mol% (G + C). Significant growth occurred only at salinities of 15 to 40% (w/v), and in the presence of at least 100 mM-NaCl, suggesting that the bacterium is indigenous to the marine environment.