- Volume 89, Issue 2, 1975

SUMMARY: Staphylococcus aureus s6 sublethally heated at 52°C for 15 min in 0·1 m-potassium phosphate buffer pH 7·2, lost neither the ribitol teichoic acid of the wall nor the glycerol teichoic acid of the membrane. Hurst et al. (1974) showed that this heating caused 40% loss of the cellular Mg, and we now report the loss of 65% of the ester-bound d-alanine of teichoic acid. Repair from sublethal heat injury, measured by the return of salt tolerance, occurs in a simple no-growth medium provided that the cell concentration is < 5 × 108/ml. During repair, d-alanine is rapidly synthesized. Fully-repaired cells contain four times more D-alanine than do freshly-injured cells. Magnesium is present in the medium at only 3 × 10−6 m, yet the cellular Mg concentration returns to normal within 1 h of incubation, even in the presence of EDTA. The results suggest that repair occurs in two stages. Soon after injury, in the absence of the competitive effect of d-alanine, Mg is strongly bound to teichoic acid. In repaired or uninjured cells Mg is less strongly bound. The implications of these findings are discussed in relation to the cation-binding function of teichoic acid.

SUMMARY: Plasma membranes were isolated from the yeast and mycelial forms of Candida albicans as described previously ( Marriott, 1975 ) and examined for the presence of several enzymes. Measurement of specific activities showed enrichment of Mg2+-dependent and Na+/K+-stimulated Mg2+-dependent adenosine triphosphatase and mannan synthetase, in the plasma membrane fractions from both morphological forms of the organism. However, acid and alkaline phosphatase, NADH oxidase and 5′-nucleotidase showed no such specific location.

SUMMARY: Only Proteus vulgaris strain pv127 out of many P. vulgaris, P. morganii and Providence strains was transduced to kanamycin resistance by high-frequency transducing variants, 5006MHFTk and 5006MHFTak, of phage 5006M, a general transducing phage for P. mirabilis strain pm5006. The phages adsorbed poorly to strain pv127 and did not form plaques. The transduction frequency of pv127 by these phages was 5 × 10−8/p.f.u. adsorbed. Phage 5006M increased the transduction frequencies. Abortive transductants were not detected. Transductants segregated kanamycin-sensitive clones at high frequency and this, together with data from the inactivation of transducing activity of lysates by ultraviolet irradiation, indicated that transduction was by lysogenization. The general transducing property of the phages was not expressed in transductions to auxotrophs of pv127. Transductants (type I) resulting from low multiplicities of phage input adsorbed phage to the same extent as pv127. This suggested a defect in the transducing particles (or host) because single phage 5006M infection converted strain pm5006 to non-adsorption of homologous phage. Type I transductants did not liberate phage, suggesting a defective phage maturation function. Transductants (type II) which arose from higher multiplicities of phage input did not adsorb phage, indicating possible heterogeneity among transducing particles. Phage derived from type II transductants adsorbed poorly to pv127 and transduced it to kanamycin resistance at frequencies similar to those of phages 5006MHFTk and 5006MHFTak, ruling out host-controlled modification as a cause of the low transduction frequencies. This phage transduced pm5006 to antibiotic resistance at high frequencies but generalized transduction was again not detected. It was suggested that general transduction could be performed by particles which, due to a different composition and/or mode of chromosomal integration, made material they carried susceptible to host-cell modification.

SUMMARY: The discovery of two mating types in the cellular slime mould Polysphondylium pallidum is reported. Two developmental mutants produced in strains of opposite mating type but which do not proceed past the aggregation stage of development are capable of producing macrocysts. These macrocysts were viable and 5 to 10% germinated after 6 weeks of storage. When the macrocyst progeny were cloned, several classes of non-parental phenotypes were recovered.

SUMMARY: Nineteen mutants of Salmonella typhimurium responding to either cysteine or methionine (cym) have been identified amongst cysteine (cys) and methionine (met) auxotrophs. Their growth responses to known intermediates in the related pathways of cysteine and methionine biosynthesis and complementation patterns in abortive transduction tests divided the mutants into six groups. Results of conjugation, cotransduction and deletion mapping experiments substantiated these groups, each of which carried a lesion within known cys genes. Enzyme assays on cym mutants from five of the six groups confirmed their cys gene deficiencies. Growth response and enzyme assay data were not consistent with cym mutants being leaky cys mutants (spared by methionine). None of eight cym mutants tested were able to convert [35S]methionine into [35S]cysteine. Selenate specifically inhibits the early enzymes of cysteine synthesis. In cym mutants this inhibition was relieved by cysteine but not by methionine, indicating that cym mutants require active cys enzymes for growth on methionine. There was evidence that methionine stimulated in vivo activity of cys enzymes in a cym mutant. Resistance to inhibition by 1,2,4-triazole results in reduced levels of the O-acetyl serine sulphydrylase. In cym mutants triazole resistance gave unstable suppression of the cym phenotype. Cym mutants may result from mutation in regulatory regions common to each of the cys genes, with the precise role of methionine as yet unknown.

SUMMARY: Random delays in cell division lead to correlations between the generation times of mothers and their daughters and to a difference between the ‘real’ and the ‘artificial’ distributions of generation times. At present there is no satisfactory relation between the two distributions although both are useful in the analysis of growth. In a special case, it is shown that they are similar as long as the coefficient of variation of generation times is small.

SUMMARY: The synthesis of β-galactosidase by an E. coli constitutive mutant was examined in a chemostat using glucose-, glycerol-, succinate- or N-limited growth media. Except for glucose-grown bacteria, the steady-state intracellular level of β-galac-tosidase was maximal at dilution rates between 0·2 and 0·3 h−1. At higher dilution rates enzyme synthesis was reduced by catabolite repression, which could be relieved by the addition of cyclic AMP. With a catabolite-resistant mutant (UV5c), no decrease in enzyme level at high dilution rates was observed. All mutants examined were constitutive and gave decreased enzyme levels at low dilution rates, with the exception of lac −/F′lac UV5c mutants where the enzyme levels rose at low dilution rates. Hyper-producing mutants were isolated but were unstable. A constitutive mutant growing on glycerol-limited media was considered the most suitable for large-scale production of β-galactosidase in a chemostat.

SUMMARY: Pieces of the fruit body of Stereum hirsutum attracted the migrating plasmodia of Badhamia utricularis at a distance of 4 cm. Extracts of fruit bodies made with organic solvents could attract, but aqueous extracts could not. Cultured mycelium and extracts of cultured mycelium also attracted strongly, but activity was not detected in culture filtrate. Phase separation with organic and aqueous phases concentrated the attractive principle. Paper chromatography indicated the presence of a single substance of high activity which migrated in isopropanol-ammonia-water with an RF of 0·83 to 0·88 and in butanol-acetic acid-water with an RF close to 0·9. The active extracts from fruit bodies and cultured mycelium were thermostable. The attractant diffused through both aqueous and gaseous phases.

SUMMARY: An extract of the basidiomycete Stereum hirsutum attracted plasmodia of Badhamia utricularis. Attracted plasmodia moved at a fairly constant speed until they contacted the source of attractant. The plasmodial front was directed towards the source by the production and advance of lobes at the nearest point of the front, and the attenuation and withdrawal of lobes in more remote parts. Directly applied extract halted the normal reversals of protoplasmic streaming in plasmodia and induced one-way flow for up to 25 min. It also caused accumulation of protoplasm, and swelling and lengthening of the treated plasmodial strands. Benzamide, a non-volatile anaesthetic, also suppressed protoplasmic flow reversals and caused protoplasm to accumulate in swellings but did not cause chemo-taxis. Extract from one other fungus, Metarrhizium anisopliae, possessed very similar activity to Stereum extract.

SUMMARY: Pseudomonas fluorescens was grown in continuous culture with glucose or NH4 + as the growth-limiting substrate. The total amount of lipid and the relative proportions of neutral lipid and phospholipid did not vary with the rate or temperature of growth. The amounts of the phospholipids, which were phosphatidyl glycerol, cardiolipin and phosphatidyl ethanolamine, altered with the type of growth limitation and with the temperature and rate of growth. A precise composition of phospholipid classes is not a requirement for growth at low temperature.

Fatty acid composition also varied with changes of these growth conditions at temperatures above 10°C, but at lower growth temperatures the degree of saturation of the lipids was strictly controlled, and was unaffected by changes in the growth rate or the nature of the growth-limiting substrate. The degree of saturation of the lipids was not critical at the higher growth temperatures, and the variation in the degree of saturation observed at these temperatures was due in part to a decreased ability of the organism to control the fatty acid composition of its lipids at temperatures above 10°C.

SUMMARY: Bacterial cultures in media with a low (0·38%, w/v) initial glucose concentration showed much smaller pH changes during growth than cultures grown in media with excess (1·25%, w/v) glucose. Increasing the concentration of the phosphate or volatile fatty acid salt (VFA salt, i.e. acetate, propionate or butyrate) in the media had no beneficial effect on cultures of Streptococcus bovis or Lactobacillus plantarum which had only minor falls in pH during growth (final pH ≥ 6·0), but increased the dry weight yield (but not the molar growth yield) of cultures which had major pH falls (final pH ≤ 4·6) during growth. The improvements in dry weight yield could be correlated with increases in the pH buffering capacity of media caused by the increased phosphate or VFA salt concentration.

The response of Bacteroides ruminicola to increases in the phosphate concentration of media was qualitatively similar to that of S. bovis. However, VFA salts (particularly acetate) always decreased both dry weight and molar growth yield. The effects of VFA salts on three other rumen bacteria, Butyrivibrio fibrisol-vens, Megasphaera elsdenii and Veillonella alcalescens, were varied. The possible mechanisms and ecological implications of the effects of these compounds are discussed.

SUMMARY: Polyacrylamide-disc gel electrophoresis and quantitative enzyme assays showed that the pathways of glucose catabolism and secondary metabolism in Penicillium expansum were dependent on the degree of aeration of the cultures. The isoenzyme patterns and specific activities of aldolase and succinate dehydrogenase indicated that glycolysis and the tricarboxylic acid cycle operated under conditions of both limited and efficient aeration (i.e. in cultures grown statically or on an orbital shaker). At high levels of aeration the growth rate was faster and synthesis of extracellular pectolytic enzymes was enhanced, whilst the activities of glucose 6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase showed that the pentose-phosphate shunt was important in glucose catabolism during the trophophase of growth. In contrast, under conditions of low aeration this latter pathway was virtually undetectable, growth was slower, pectolytic enzyme production low and large concentrations of secondary metabolites (6-methylsalicylic acid, patulin and citrinin) accumulated.

SUMMARY: The effect of chlorine on the germination, outgrowth, colony formation and structure of spores of Clostridium bifermentans, Bacillus subtilis var. niger and Bacillus cereus was examined. Chlorine decreased heat resistance and slowed or prevented germination and swelling, but spores that did swell were usually able to elongate to form vegetative cells. Chlorine removed protein from spores, apparently from the coat, and allowed lysozyme to initiate germination. Treatment with other agents that remove spore-coat protein increased the lethal effect of chlorine by as much as 4000-fold, suggesting that coat protein protects spores against chlorine.