- Volume 59, Issue 2, 1969

SUMMARY: Temperature, salinity and pH optima of the marine bacterium Leucothrix mucor were determined directly in nature by use of tritiated thymidine auto-radiography and compared with the same characteristics of laboratory cultures. Field studies were done in Puget Sound, Washington, U.S.A., and Loch Ewe, Scotland. The temperature optima of cultures isolated from various sea-coast areas around the world were 28°, irrespective of the temperature of the habitat from which the culture was derived. In contrast, the temperature optima in the natural environment were significantly lower, ranging from 6.5° to 25°, depending on the habitat studied. Attempts to obtain physiological adaptation of laboratory cultures to low temperature failed. The results emphasize the danger of inferring the response to temperature of natural populations from the characteristics of laboratory cultures. In contrast, responses to salinity and pH optima in natural environments were the same as those of laboratory cultures.

SUMMARY: With a glucose-limited chemostat culture of Azotobacter vinelandii iam 1078 the yield factor, , for glucose increased from 0.3 to 0.12 following an increase in the dilution rate from 0.1 to 0.35 hr−1. However, even when growing at the faster rate the value of still was extremely small compared to those found with other micro-organisms. This low yield value was not due to an incomplete oxidation of glucose, since most of the glucose carbon utilized (83 to 97%) could be accounted for as carbon dioxide, the percentage conversion depending on the dilution rate. The specific respiration rate ( ) of the growing culture was determined in situ and found to remain nearly constant over the range of dilution rates. However, the value of diminished progressively from 0.12 to 0.03 when the dissolved oxygen concentration in a chemostat culture was increased from 3.3 to 5.7 p.p.m. The yield factor, Y ATP (evaluated by making certain assumptions) was much smaller than the value of 10 found with other microbial culture, even though the value of Y ATP increased appreciably with the increase of dilution rate. These results are discussed with reference to some of the known physiological characteristics of A. vinelandii.

SUMMARY: The stability of penicillinase messenger RNA has been assessed from the kinetics of enzyme production after inhibition of RNA synthesis with actinomycin or rifampicin. An average messenger half-life of 4.7 min. is indicated, both for induced Bacillus licheniformis 749, and the constitutive mutant 749/c. Although this value is twice that estimated for average total m-RNA by similar techniques, there is no indication of a ‘long-lived messenger’ as previously implicated in other reports. An attempt was made to estimate the content of penicillinase messenger from data on the level of penicillinase made per bacterium, the polysome size, the messenger half-life and the total level of unstable RNA per bacterium. It is suggested that at the maximum induced rate of enzyme formation there are approximately 110 penicillinase messengers per bacterium, and in the constitutive about twice this number.

SUMMARY: The effect of irradiating donor cells, immediately before mating, upon the yield of recombinants has been investigated for male (F+ + Hfr) strains of Escherichia coli, which, owing to a mutational block (uvr), are unable to excise pyrimidine photoproducts. Despite the extreme sensitivity of the uvr − strains employed, as judged by colony formation, the yield of recombinants was surprisingly little affected by u.v. In particular, using an Hfr uvr b − strain it was found that, after an initial fall to about 30–40% of that given by the unirradiated control, the yield of recombinants for both early and late markers declined with increasing dose at about the same rate as for the parent uvr + strain. There was evidence of damage in the DNA transferred from irradiated males in that normal linkage of unselected markers was reduced, but the decline in linkage with increasing dose was the same for both uvr + and uvr − strains. The yield of recombinants was nearly independent of the uvr phenotype of the F − parent. Thus although fertility and survival are closely correlated in the uvr + Hfr, this correlation disappears in the uvr − male. Instead the u.v. sensitivity of the processes involved in chromosome transfer appears only slightly altered in these mutants despite the considerable change in sensitivity as judged by colony-formation.

SUMMARY: Soluble serologically active preparations extracted by various methods from Saccharomyces spp. showed the group specificity previously detected by agglutination tests with whole cells. The antigenic properties of the four serological groups of the genus Saccharomyces are probably determined by the cell wall mannan.

SUMMARY: Five streptomycins bleached the chloroplast system of Euglena gracilis; the most effective were those which contained an aldehyde group in the streptose moiety: streptomycin and hydroxystreptomycin. Derivatives containing a secondary alcohol group in place of the aldehyde (dihydro-, dihydro-desoxy-, dihydrohydroxystreptomycin) require higher concentrations to elicit the same effect. Hydroxylamine reversed the bleaching effects of streptomycin and hydroxystreptomycin but not of dihydro-, dihydrodesoxy- or dihydrohydroxystreptomycin. These observations suggest that the aldehyde group of the streptomycins contributes to the action of these antibiotics on Euglena chloroplasts; the action of hydroxylamine would be to either remove the antibiotic from its site of action or to render it ineffective in vivo by reaction with the aldehyde group.

SUMMARY: The concentrations of three enzymes active in ammonia assimilation by Rhizobium japonicum (glutamate dehydrogenase, aspartate aminotransferase, alanine aminotransferase) were influenced considerably by the N-source in the culture medium. Relatively high concentrations of these enzymes were present when R. japonicum was grown in a medium containing NH4Cl + 2-oxoglutarate. Relatively low amounts of these enzymes were found in bacteria grown in the presence of various amino acids. Active protein and RNA synthesis were necessary for the induction of the enzymes by NH4Cl + 2-oxoglutarate.

SUMMARY: The lipid content and fatty acid composition of sporangiospores and vegetative mycelium of mesophilic, thermotolerant and thermophilic fungi in the Mucorales were examined. In each fungus the spores contained less lipid than the vegetative mycelium. The mesophiles accumulated less lipid in spores and mycelium than did thermotolerants and thermophiles. No unusual fatty acids were detected by gas-liquid chromatography in the lipids of spores or mycelium. The fatty acid compositions of spores and vegetative mycelium were qualitatively very similar, but spore lipids were always more highly saturated than mycelial lipids. Lowering growth temperature from 48 to 25° increased the synthesis of unsaturated fatty acids in the spores and the mycelium of the thermotolerant and thermophilic fungi examined.

SUMMARY: Isolated bacterial wall material from four Gram-positive and four Gram-negative organisms bound crystal violet as well as or better than intact bacteria. Dye binding ability varied between species. There was no correlation between the dye binding ability of isolated wall material and the Gram characteristics of the intact bacteria.

SUMMARY: Mycelium of potassium-limited Neocosmospora vasinfecta had a lowered potassium content and an increased sodium content compared with mycelium grown in presence of excess potassium and no sodium. Potassium uptake involves the exchange for Na+ and probably also for H+.

Total potassium uptake was decreased to half by a fivefold equivalent excess of rubidium, but was essentially unaffected by a 100-fold equivalent excess of sodium. Calcium and magnesium had intermediate effects. Potassium uptake was inhibited by sodium azide (mm) and by dinitrophenol (0.3 mm). These depressed the equilibrium potassium level but had a much smaller effect on the time required to reach equilibrium. Loss of potassium by K+-loaded mycelium to sodium azide or dinitrophenol solutions or to water was small. Much greater losses occurred to solutions of rubidium but not of sodium.

It is suggested that the equilibrium potassium level is determined only in part by exchange-diffusion at the mycelium surface, and that net potassium uptake is a metabolic process.

SUMMARY: A latent, non-specific phosphatase of Hartmannella castellanii with an optimum pH of 4·0 has been investigated. The latency could be released in cell-free homogenates by treatment with Triton x 100, freezing and thawing, refrigeration or carbon tetrachloride. It seems likely that this enzyme is attached to a sub-cellular organelle as it was largely sedimentable when homogenates were prepared in media containing sucrose.

During encystation of the amoebae under controlled conditions there was no appreciable change in the levels of total phosphatase activity measured in frozen-thawed extracts, but there were quite large increases in free activities of fresh, unfrozen preparations. Inhibitors and promoters of encystation were also found to affect the levels of phosphatase activity in the amoebae but did not affect its sedimentability which persisted throughout the initial degradative phase of encystment.

Incubation of homogenates of Hartmannella decreased the latency of the acid phosphatase but this activation could be modified by substances which are known to affect the encystation responses of the amoebae.

It is concluded that the degradative phase of encystation is due to the activation of hydrolytic enzymes within sedimentable compartments of the amoebae and is not the result of hydrolases being released from these compartments. It seems likely that agents which are capable of promoting encystation may do so by inducing activation of lysosomal enzymes.

SUMMARY: Various strains originally designated as members of the genera Micrococcus, Sarcina, and Staphylococcus were able to transform adenine, histidine, and tryptophan auxotrophs of Micrococcus lysodeikticus to prototrophy at relatively high frequencies. These included certain strains of M. flavocyaneus, M. flavus, M. luteus, M. lysodeikticus, M. sodonensis, Sarcina flava, S. lutea, S. subflava, Staphylococcus afermentans and St. flavocyaneus. Many of the above strains were adenine auxotrophs and produced low frequencies of prototrophic recombinants when crossed with the adenine-dependent M. lysodeikticus strain isu. Prototrophic strains of M. conglomeratus, M. radiodurans, M. roseus, M. rubens, M. varians, St. aureus and St. epidermidis failed to transform M. lysodeikticus in these studies. Prototrophic pigment mutants of M. lysodeikticus and S. lutea were able to doubly transform yellow auxotrophs of M. lysodeikticus to prototrophy and donor colour.

SUMMARY: Fluorescence and chromogenic cytochemistry confirmed the presence of -SH groups in the walls of Candida albicans and C. utilis, predominantly at budding sites. They were absent from pseudomycelia of C. albicans and the walls of the mycelium and the hyphal tips of Penicillium notatum but present in the walls of the tips of the phialides of P. notatum. Autoradiography after treatment with tritiated SH-blocking agents confirmed these findings.

SUMMARY: Pseudomonas aeruginosa grown under conditions of Mg-depletion in batch eulture in simple salts medium lost sensitivity to polymyxin B, causing lysis, release of 260 nm. absorbing materials and loss of viability. The patterns of lysis and leakage produced by polymyxin were similar with regard to the effect of growth in different Mg concentrations and the inhibitory effect of high polymyxin concentrations. The rates of lysis and leakage for any one suspension were similar. There was decreased polymyxin uptake by insensitive bacteria. Addition of Mg or one of several cations restored sensitivity both to polymyxin and to EDTA to varying degrees, but only after several cell divisions had occurred. A close similarity was observed between the effects of Mg-depletion on sensitivity to EDTA and to polymyxin; a relationship between their mechanisms of action is suggested. It is proposed that cations are essential for the synthesis of sensitive components of the envelope and may themselves be involved in the structure of the component.

SUMMARY: The mean volume of a diploid spore population is twice that of a haploid spore population; it is assumed that the mean volume of an aneuploid spore population is a similar reflexion of its ploidy. The distribution of volumes amongst a population of spores of Dictyostelium discoideum was analysed in terms of frequency of occurrence of diploid, aneuploid and haploid cells; in a wild-type strain (nc-4) these cell types were present in the ratio 8:3:89. It is suggested that ‘metastable’ strains are mutants in which this ratio has been altered.

SUMMARY: An inducible sucrose hydrolysing enzyme has been found in Bacillus subtilis. The enzyme is intracellular, unstable in the absence of EDTA and its formation is repressed by glucose. These properties contrast with those of the levan-sucrase enzyme previously investigated in this organism.