Summary: A radiorespirometric study of glucose metabolism in Candida utilis CBS 621 was done using glucose-limited chemostat cultures growing at a dilution rate of 0.1 h−1 with ammonium or nitrate as the nitrogen source. From a steady-state analysis of 14CO2 yields from [1-14C]- and [6-14C]glucose supplied in the medium feed it appeared that during growth with nitrate the flow of glucose through the hexose monophosphate (HMP) pathway was much higher than during growth with ammonium as the nitrogen source. The same phenomenon was apparent from an analysis of the rate of 14CO2 production after administration of small amounts of labelled glucose to samples withdrawn from steady-state cultures. Additionally, these experiments revealed not only that the initial fraction of glucose 6-phosphate routed into the HMP pathway increases, but also that recycling of hexose phosphates via this pathway increases when nitrate is used as the nitrogen source. From a quantitative analysis of the results it is concluded that the contribution of the HMP pathway to glucose metabolism is close to the theoretical minimum required to cover the NADPH requirement for biosynthesis.
Summary: Escherichia coli K12 and Salmonella typhimurium LT2 cells were stabilized during carbon starvation in the presence of peptidase-deficient mutant strains. The rate of loss of viability of the wild-type S. typhimurium strain was decreased an average of 2-fold, and the rate for the wild-type E. coli strain was decreased about 2.3-fold, when either was starved in the presence of the multiply peptidase-deficient S. typhimurium strain TN852; other peptidase-deficient strains exhibited similar stabilizing effects. Starving wild-type S. typhimurium LT2 cells utilized peptides excreted by the starving peptidase-deficient cells for protein synthesis, and, to a lesser extent, as respiratory substrates. Provision of free amino acids in steady-state levels to starving E. coli K12 cells in a cell recycle apparatus had a stabilizing effect similar to that of mixing with peptidase-deficient cells.
Summary: Pseudomonas saccharophila Doudoroff (ATCC 15946) reduced C2H2 and fixed 15N2 heterotrophically in N-free semi-solid medium supplemented with 100 mg yeast extract l−1. Nitrogenase activity was markedly stimulated by addition of sugars and organic acids and was expressed microaerobically. Autotrophically-grown cells showed nitrogenase activity. This is the first report of N2 fixation in a well-characterized Pseudomonas species capable of chemoautotrophic growth with H2 as the electron donor.
Summary: In sugar-grown cells of cowpea Rhizobium strain NGR234 activities for enzymes of the Entner-Doudoroff and pentose phosphate pathways were present while the virtual absence of phospho-fructokinase and fructose-bisphosphate aldolase indicated that the Embden–Meyerhof–Parnas pathway was unlikely to be significant. Invertase, fructokinase, glucose-6-phosphate dehydrogenase and the Entner–Doudoroff enzymes were present at only low activities in succinate grown cells, but were induced in sugar-grown cells. Isolated snakebean bacteroids contained very low activities of these four enzymes. Although C4-dicarboxylic acids exerted some repressive effect on induction of these enzymes, there was substantial enzyme activity induced in cells grown on sucrose plus a C4 dicarboxylic acid. The data suggest that the peribacteroid membrane may be relatively impermeable to sugars and so dictate the carbon source(s) available to the bacteroids.
Summary: Regeneration of protoplasts to bacilli was attempted in several strains of Bacillus closely related to Bacillus subtilis 168. On DM3 and similar media using succinate as osmotic support, only B. subtilis 168 and Bacillus natto ATCC 15245 were able to regenerate. Media containing mannitol as osmotic support, and agar as gelling agent gave rise to L-form colonies with Bacillus licheniformis NCTC 6346. Many of the L-form colonies were able to regenerate to the bacillary form when plated on the mannitol medium solidified with gelatin. All of the Bacillus species tested were able to regenerate on the latter medium at rates sufficient to allow protoplast transformation and fusion experiments.
Summary: [14C]Methylamine uptake by free-living Rhizobium sp. ANU289 had Michaelis–Menten kinetics (apparent K m 6.6 μm). Uptake was competitively inhibited by ammonia (K i 0.4 μm) and was dependent on an energized membrane. Uptake by bacteria had an optimum at pH 7.0. Methylamine uptake by bacteroids from siratro root nodules was much slower than that by free-living bacteria at pH 7.0 but increased exponentially with the pH of the medium. Uptake by bacteroids did not show saturation kinetics and was insensitive to the presence of ammonia or uncouplers. These results suggest that free-living bacteria (grown under conditions where ammonia is limiting) have an active transport mechanism for the uptake of ammonium ions; this carrier is not operative in the symbiotic state, where passive diffusion of ammonia occurs. In the free-living state, the ammonium carrier is under genetic control, being repressed by growth on high concentrations of ammonia. Derepression occurs under conditions of nitrogen starvation.
Summary: One non-xerophilic fungus, Penicillium digitatum, and four xerophilic fungi, Penicillium janczewskii, Eurotium chevalieri, Wallemia sebi and Polypaecilum pisce, were grown at six different water activities (a w) on media containing various concentrations of sodium chloride. Each species was sampled as soon as visible growth appeared and up to six times thereafter during various stages of the growth cycle. The fungal mycelium was extracted and assayed for glycerol using a specific enzymic method. At the highest a w, 0.997, only small amounts of glycerol were present in the fungi. At lower a w values, glycerol concentrations rose rapidly at first, then declined as the cultures aged. There appeared to be a correlation between the amount of glycerol accumulated, and the complexity of the spore-bearing structures. Glycerol depletion appeared to be related to the formation of spores and their maturation.
Summary: The activities of several enzymes of polymyxin B-treated dormant and germinated spores of Bacillus subtilis were examined. The particulate NADH oxidase of the antibiotic-treated spores showed considerably lower specific and total activities compared with those of untreated ones. The specific and total NADH oxidase activities of untreated spores increased 12- and 15-fold respectively during germination, whereas increases during germination of polymyxin B-treated spores were inhibited. The specific and total activities of particulate NADH cytochrome c reductase of dormant spores were decreased by polymyxin B treatment in almost the same proportion as those of the particulate NADH oxidase. The specific activity of NADH dehydrogenase of dormant spores remained unchanged after antibiotic treatment but the total activity fell considerably. The activities of other enzymes examined were similar for untreated dormant and germinated spores and antibiotic-treated spores. The respiration of polymyxin B-treated dormant spores was inhibited at the same time as the start of germination. Morphologically, polymyxin B-treated dormant spores lost a laminar structure of the cortex and details of the spore protoplast. The inhibitory mechanism of particulate NADH oxidase activity of polymyxin B-treated dormant spores is discussed.
Summary: Intact cells of phosphate-depleted Phaeodactylum tricornutum possessed non-specific alkaline phosphatase (EC 188.8.131.52; PMEase) and 5′-nucleotidase (EC 184.108.40.206; 5′-NDase) activities; there was also an extracellular PMEase. The optimum pH for the cell-bound PMEase was > 10.3, and for the 5′-NDase was 9–9.5. The extracellular PMEase had an optimum pH > 10.3 and accounted for > 30% of the total PMEase activity at this pH; there was no extracellular 5′-NDase activity. The activities of these enzymes increased during phosphate-deprivation, but the rate of AMP hydrolysis (by the action of both PMEase and 5′-NDase) always exceeded that of p-nitrophenylphosphate at the physiological pH (for a marine organism) of 8–8.5. By the use of differential centrifugation after cell disruption in a French pressure cell, a highly purified fraction of cell walls was prepared. This fraction was virtually devoid of membranous material as viewed by electron microscopy, and exhibited PMEase, but no 5′-NDase activity. By using a different centrifugation procedure after disruption by shaking with glass beads, a microsomal fraction (pelleted by forces of 14000–156000 g) was prepared. This fraction was free of cell wall fragments as viewed by electron microscopy, and exhibited 5′-NDase activity but no PMEase activity. It is concluded that the PMEase was associated with cell walls, whilst the membrane-bound 5′-NDase which sedimented as vesicles in the microsomal fraction was associated with plasma membranes.
Summary: Aerial mycelium formation by Streptomyces sp. MA406-A-1, a formycin-producing strain, was suppressed by the presence of excess nutrient. In such suppressed cultures, decoyinine, which specifically inhibits GMP synthetase, initiated the formation of aerial mycelium at concentrations which only partially inhibited growth. The intracellular GTP pool of organisms growing in liquid culture markedly decreased on the addition of decoyinine. Decoyinine was also effective in initiating aerial mycelium formation of three other Streptomyces spp. examined. Regardless of the successful initiation of aerial mycelium formation, the ability of the cells to produce antibiotics (formycin or actinomycin D) did not increase, but decreased, on the addition of decoyinine. It is concluded that aerial mycelium formation by Streptomyces results from a decrease in the pool of GTP (or GDP), whereas antibiotic synthesis results from a different signal(s).
Summary: Mutants of the gliding bacterium Cytophaga johnsonae that are incapable of movement are called truly nonmotile (TNM) to distinguish them from other mutants that are motile but produce nonspreading colonies. All TNM mutants are pleiotropic, being nonmotile, unable to digest chitin, resistant to all phages that infect wild-type cells, nonadherent and having less hydrophobic surfaces than do wild-type cells. In this study, we tested the idea that the TNM pleiotropy is the result of blocking cell surface movement, rather than of loss or alteration of a specific cell surface component. Motility of wild-type cells was blocked by addition of chemicals, and treated cells were compared with untreated cells for their ability to adhere to spheroidal hydroxyapatite (SHA) beads and to adsorb phages, two characteristics used as an index of the TNM pleiotropy. All the chemicals tested that blocked motility also reduced phage adsorption and adherence to SHA to approximately the same extent seen with TNM mutants. The chemicals tested (carbonyl cyanide m-chlorophenylhydrazone, cyanide, azide and photoactivated eosin Y and rose bengal) were sufficiently different from each other to reduce the possibility that each chemical inhibited phage adsorption and cell adherence by similar secondary effects, independent of their effects on motility. It was also shown that the pleiotropy of TNM mutants is not caused by their inability to maintain a membrane potential. The results are compatible with the conclusion that the TNM pleiotropy is manifested whenever cell movement is stopped, whether by mutation or by use of chemical inhibitors, and they are inconsistent with the idea that all TNM mutants are pleiotropic because they all carry a lesion in the same gene that codes for expression of surface components required for all characteristics affected. The reason that stopping motility influences several seemingly unrelated properties is not known but is probably related to adaptations required for the organism to interact with its environment through a cell surface covered with a slime that is normally kept in motion by components of the machinery of gliding motility.
Summary: Populations of Saccharomyces cerevisiae NCYC 431, harvested after 16 h incubation from self-induced anaerobic cultures, were more tolerant to the inhibitory effect of ethanol on fermentation rate and viability than organisms harvested from 8 h cultures. Ethanol increased the rate of passive influx of protons into de-energized organisms at a rate which was greater with organisms from 8 h compared with 16 h cultures. Rates of passive influx of protons into spheroplasts were significantly greater than into intact organisms, although culture age did not affect rates of ethanol-induced influx of protons into spheroplasts. Ethanol retarded both the initial net rate of proton efflux and the final extent of acidification produced by suspensions of energized organisms, both effects being more pronounced with organisms from 8 h as compared with 16 h cultures. The magnitude of the proton-motive force (Δp) was decreased by ethanol in both energized and de-energized organisms. Although culture age did not affect the extent of ethanol-induced decrease in Δp in de-energized organisms, in energized organisms harvested from 8 h cultures ethanol produced a significantly greater decrease in Δp as compared with organisms from 16 h cultures. If the ability of ethanol to decrease the Δp value is important in its inhibitory effect on growth, it is suggested that some phenomenon other than proton uncoupling is involved.