- Volume 131, Issue 12, 1985

Summary: Anabaena variabilis (ATCC 29413) grown in batch cultures for 2 d exhibited rapid glycogen synthesis upon dilution of the cell suspension. The cellular polysaccharide concentration attained a maximum after 9-12 h growth in fresh medium and decreased thereafter. The growth rate, the rate of glycogen accumulation and the maximum amount of glycogen increased when light intensity was increased. Accumulation occurred with both N2 and ammonia as N-sources. In cultures grown in the presence of ammonia, the increase in the cellular C-fraction upon dilution caused neither induction of nitrogenase nor heterocyst formation. However, ammonia depletion during subsequent growth gave rise to a second accumulation of glycogen followed by differentiation. Thus, in this phototroph, glycogen is synthesized without subsequent differentiation following an increase in average irradiation as long as the N-supply is maintained. Glycogen synthesis following N-depletion, however, is accompanied by induction of nitrogenase.

Summary: When a Cd-resistant strain (301 N) and a Cd-sensitive strain (101 N) of Saccharomyces cerevisiae were incubated in medium containing Cd2+, a large proportion of the cellular Cd2+ was found in the cytosol of strain 301 N, but not in that of strain 101 N. Approximately 65% of the cellular Cd2+ was released from strain 301 N after treatment with chitosan, which affects cell membrane permeability. About 80% of the cellular Cd2+ released from strain 301 N by chitosan treatment was detected in a 30000-10000 molecular weight fraction prepared by ultrafiltration. The distribution of Cd2+ into the cytosol in strain 301 N was inhibited in the presence of cycloheximide. The proportion of cellular Cu2+ or Zn2+ present in the cytosol after incubation with these ions was similar for the two strains (about 40%).

Summary: Addition of glucose to acetate-grown cells of Saccharomyces cerevisiae caused a rapid transient increase in the cAMP level followed by a 10-fold, transient increase in the activity of trehalase. Exhibition bromide and acridine analogues inhibited both glucose-induced responses in a similar way, confirming the role of the cAMP signal as the second messenger in the sugar-induced activation of trehalase. When nitrogen sources or protein synthesis inhibitors were added after the transient glucose-induced increase in the trehalase activity, a rapid reactivation of trehalase occurred. In this case, however, there was only a very small increase in the cAMP level, which appeared to be insignificant. When the nitrogen source or the protein synthesis inhibitor was added together with glucose, the trehalase activity remained high for a much longer time also without a significant effect on the cAMP level. When a membrane depolarizing agent was added together with the glucose, both the trehalase activity and the cAMP level remained high. Reversibility experiments in which trehalase was activated to different degrees also showed that for high sugar-induced trehalase activation a high cAMP level is needed, while nitrogen sources stimulate trehalase activity without affecting cAMP levels. In cell extracts, both cAMP and cGMP were able to activate trehalase, the latter however only at 10-fold higher concentrations. The cGMP level in vivo was about 10-fold lower than the cAMP level and was not significantly affected by nitrogen sources or protein synthesis inhibitors. Hence, neither cAMP nor cGMP seem to be involved as the second messenger in the stimulating effect of nitrogen sources and protein synthesis inhibitors on trehalase activity in yeast. Since all other evidence obtained here and before strongly points to regulation of trehalase by a ‘cAMP-dependent’ protein kinase, we suggest that the presence of a nitrogen source in the growth medium of yeast induces the rapid synthesis of an alternative second messenger able to activate this or another protein kinase.

Summary: Octyl β-D-glucopyranoside prevented the expression of cell-associated fructosyltransferase activity in Streptococcus salivarius ATCC 25975 grown in batch culture or incubated in non-proliferating cell suspension medium. This effect was not due to the direct inhibition of enzyme activity nor due to the loss of active enzyme into the external medium. The prevention of enzyme expression did not appear to be due to the inhibition of a general translocation mechanism for protein secretion, since fructosyltransferase activity was not detected within the cytoplasm of lysed cells grown in the presence of octyl β-D-glucopyranoside; nor was there any observed inhibition of the secretion of the extracellular enzyme glucosyltransferase. These and other observations supported the view that fructosyltransferase was not secreted across the cytoplasmic membrane in an active form before becoming associated with the cell surface.

Summary: Escherichia coli cells carrying fosfomycin-resistance plasmids show high levels of resistance towards this drug. However, the plasmid-carrying strains exhibited a transient lytic phase induced by fosfomycin when grown in rich liquid media. This lytic phase was not observed if the cells were grown in liquid minimal media. Fosfomycin-induced lysis depended on the accumulation of drug inside the bacteria, presumably as a result of the saturation of the fosfomycin modification system. Growth recovery after lysis was not due to drug inactivation in the culture medium and could be explained by selection of mutants showing impaired fosfomycin transport when high concentrations of fosfomycin were used. However, there was no selection of mutants with low drug concentrations.

Summary: Methanogenic bacteria with pseudomurein sacculi incubated with elevated concentrations of amino acids showed growth inhibition, changes in morphology and, under certain conditions, lysis. Methanobacterium thermoautotrophicum incorporated the amino acids glycine, threonine, ornithine and, in small amounts, aspartic acid into the sacculi, but not D-alanine, meso-diaminopimelic acid or the amino sugar galactosamine.

Summary: Ethanol is the first reported compound which can induce germ tube formation in Candida albicans without the addition of any nitrogen-containing nutrients. Conditions controlling induction of germ tubes in C. albicans by ethanol were investigated. Ethanol (17.1 mM) in buffered salts solution containing sodium bicarbonate induced 70 to 80% of yeast phase cells of C. albicans to form germ tubes. Germ tubes could be induced by ethanol (0.08 to 340 mM) at temperatures ranging from 29 to 41 °C (optimum 37 °C) and at pH values ranging from 3.0 to 8.0 (optimum 5.75). The germ tubes averaged 11 μm in length after 6 h at 37 °C. The percentage of cells forming germ tubes decreased as the concentration of cells in the induction solution was increased above 4 x 105 cells ml−1. Germ tubes first appeared 45 to 60 min after continuous exposure to ethanol at 37 °C and all cells which formed germ tubes did so by 2 h. Germ tube length decreased as the pH was increased but was independent of the concentration of ethanol. Oxygen was required for germ tube formation. In addition to ethanol, 1-propanol, 2-propanol, 1-butanol and acetic acid could induce germ tube formation, whereas methanol could not. These results indicate that the cells must mobilize their endogenous nitrogen and probably carbohydrate reserves in order to initiate formation of germ tubes. The evidence is inconclusive as to whether ethanol itself must be metabolized for germ tube induction to occur, although it is not thought to act by a nonspecific interaction with the cell membrane.

Summary: Esterases, and glutamate, lactate and malate dehydrogenases of 64 Aeromonas hydrophila, A. caviae and A. sobria strains, were analysed by polyacrylamide agarose gel electrophoresis and by thin layer isoelectrofocusing. On the basis of the isoelectric points of malate dehydrogenase from the three species and the mobility of lactate dehydrogenase from A. sobria, 8 species specific zymotypes were defined: three for A. hydrophila strains, three for A. caviae strains and two for A. sobria strains. These zymotypes correlated with previously established DNA hybridization groups. The other electrophoretic data were found to be less useful for distinction between A. hydrophila and A. sobria strains, but supported differentiation into zymotypes for A. caviae strains. The two-dimensional electrophoretic profile established by plotting isoelectric point against electrophoretic mobility of the major esterase illustrated the degree of enzyme polymorphism among the strains of the three species. Variation in electrophoretic patterns within A. hydrophila and A. caviae might provide useful epidemiological markers.

Summary: Muramidase digests of alkali-treated SDS-insoluble peptidoglycan from two strains of Neisseria gonorrhoeae were examined. Both strains contained disaccharide peptide monomers that had intramolecular 1,6-anhydro-muramyl ends. In contrast to strain 1L260, in which 50% of the monomer fraction is O-acetylated, the monomer fraction from strain RD5 was completely devoid of O-acetyl groups, as shown by HPLC. Penicillin decreased the O-acetylation of peptidoglycan but did not affect the proportion of anhydro-muramyl residues.