- Volume 83, Issue 2, 1974

Summary: Membrane vesicles of Thiobacillus neapolitanus take up amino acids at 25 °C in the presence of the nonphysiological electron donor, ascorbate- N,N,N′,N′-tetramethyl- p -phenylenediamine. The amino acids accumulate inside the membrane vesicles against a concentration gradient. Inhibitors of the electron transport chain inhibit the accumulation; therefore active transport of amino acids in T. neapolitanus is coupled to the electron transport chain. The Km values for the transport of glycine and l-serine in this organism are 2·5 and 5 μ m respectively.

SUMMARY: Mannans isolated from Kluyveromyces species, from their imperfect forms Candida pseudotropicalis and Torulopsissphaerica, and from Saccharomyces species were examined for their reactivities with Kluyveromycesfragilis and Saccharomyces cerevisiae antisera. It was found that Kluyveromycesfragilis, K. marxianus,K. lactis, Candida pseudotropicalis and Saccharomyces chevalieri possessed a specific antigenic mannan which after acetolysis yielded fragments up to pentasaccharide. Moreover these mannans showed high cross-reactivity with S. cerevisiae antiserum that could have been caused by the presence of a determinant group common to Kluyveromyces and Saccharomyces species. Polysaccharides obtained from K. polysporus and K. drosophilarum showed different immunological properties from the former mannans.

SUMMARY: The most abundant fatty acids of Caulobacter crescentus, as determined by gas- liquid chromatography, were 18: 1, 16: 1, 16: 0, 12: 0, 15: 0, 17: 0 and cyclopropane acid 17Δ. The composition of the two morphological forms of this bacterium differed, in that the stalked bacteria and isolated stalk fragments contained more 16: 0 and 17 Δ, and less 16:1 than the swarmers.

SUMMARY: Hyphal wall preparations of Schizophyllum commune were treated with enzymes and the dissolution of wall components and the degradation of septa were simultaneously recorded. The breakdown of the alkali-insoluble R-glucan (β-1,3, β-1,6-glucan) by R-glucanase was not influenced by the presence of chitinase but the breakdown of chitin by chitinase was stimulated by R-glucanase. The combination of R-glucanase and chitinase also had a synergistic effect on crosswall degradation. This indicates that the crosswalls contain both chitin and R-glucan, the chitin probably embedded in R-glucan. S-glucan (α-1,3-glucan), a prominent component of the lateral walls, is apparently absent from the crosswalls. The septal swellings consist of material that is alkali soluble but different from S-glucan. Crosswalls in hyphal wall fragments from a dikaryon were much more resistant to enzymic dissolution than those in hyphal wall fragments from a monokaryon. Such a difference could not be noted in the dissolution of wall components. The results are discussed with regard to their significance for sexual morphogenesis in Schizophyllum commune

SUMMARY: Mycoplasma dispar has been shown to produce a capsule which can be visualized by electron microscopy following staining with ruthenium red. The capsule of M. dispar possesses no obvious structure and extends for 17 to 24 nm beyond the cytoplasmic membrane. Ruthenium red also stains the capsule of M. mycoides var. mycoides so that it can be seen by electron microscopy. Five other bovine mycoplasmas, M. agalactiae var. bovis, M. bovigenitalium, M. bovirhinis, Acholeplasma laidlawii and a T-mycoplasma, and one human mycoplasma, M. pneumoniae, were found not to produce a capsule.

Summary: Intraspecific transformation in three strains of Pseudomonas fluorescens was observed with respect to gelatin liquefaction and chlortetracycline resistance. In interspecific transformation experiments involving 23 pairs of strains and four markers, two yielded positive results: a strain of P. fluorescens acquired the property of gelatin liquefaction when transformed with P. aeruginosa DNA, and a strain of fish Pseudomonas, incapable of growing at 37 °C, did so when transformed with DNA from another strain of P. aeruginosa. The guanine-cytosine content of the DNA of the strains investigated ranged between 61·0 and 64·4 mol %. The transforming ability of DNA was destroyed by DNase. The divalent ions Mg2+, Ca2+ and Ba2+ improved transformation frequency several fold. Actinomycin D inhibited transformation.

SUMMARY Donor and recipient strains were isolated from a single clinical isolate of an Escherichia coli O4. Strain z20 is a low-frequency donor which transfers a variety of markers to the recipient strain, cf2004-6. However, the recombination frequency for the tryptophan marker occurs at a somewhat higher frequency. The fact that all recombinants become donors and donor ability can be temporarily derepressed, suggests that this intra-strain conjugation system depends upon a repressed sex factor, termed the Z factor. When a lysogenic donor strain is used, the phage genome also is transferred during conjugation to a majority of the recombinants. This leads to a state of ‘transient lysogeny’ in which all recombinants segregate non-lysogens.

SUMMARY In some nisin-producing strains of Streptococcus lactis, clones which were permanently incapable of producing nisin (Nis−) appeared spontaneously with a frequency of 0·03 to 0·82 %. Treatment with proflavin (Pro), ethidium bromide (EB) or at a temperature of 40 °C increased the number of such clones. In one strain 78 % of cells became Nis− after treatment with Pro.

Treatment with nitrosoguanidine did not reverse the effect of Pro or EB. There was no evidence that Pro or EB selected spontaneously-occurring Nis− clones.

These observations suggest that the gene(s) responsible for nisin production in some S. lactis strains may be located on a plasmid, but further investigation is required to confirm this.

SUMMARY: Under conditions of limited-adenine supplementation, 8-azaguanine is a potent inhibitor of purine auxotrophic strains of Neurospora crassa. It is relatively ineffective in prototrophic strains. Spontaneous and u.v.-light-induced mutants, resistant to 8-azaguanine, were obtained in a strain carrying the ad-2, ad-3A, and ad-3B markers. The resistant mutants grew in the presence of 200 μg 8-azaguanine and 2·0 μg adenine sulphate/ml medium. Inhibition of the sensitive strain is virtually complete under these conditions. Higher adenine sulphate concentrations prevent inhibition of the sensitive strain by 8-azaguanine. Resistance of the new mutants to 8-azaguanine was demonstrated by growth-tube experiments and by plating efficiencies in the presence and in the absence of the inhibitor. Growth-tube experiments were also used to study the reversal of 8-azaguanine induced inhibition by adenine sulphate. The resistance markers in the five strains studied were assigned to linkage group III. The locus designation aza-3 was given to the resistance marker in a selected mutant of spontaneous origin. Resistance to 8-azaguanine is stable in the presence and in the absence of the inhibitor. In heterokaryons, 8-azaguanine resistance is recessive.

Summary: The cell volume and macromolecular composition, in terms of DNA, RNA and cell mass, were examined in Anacystis nidulans at different growth rates of the organism. Both DNA and RNA increased exponentially with increasing growth rate, as has been found in several heterotrophic bacteria. However, in this blue- green alga the ratio of DNA to RNA was independent of growth rate. Cell mass and volume also increased exponentially with growth rate though at a slower rate than RNA and DNA. These results also indicate a constant ratio of tRNA and rRNA to DNA in contrast to the situation in heterotrophic bacteria so far studied.

The variation of cell volume in this organism can be related to the control of cell division, and indicates that the commencement of DNA replication and the processes of cell division are associated with the achievement of a critical cell volume, as has been demonstrated for Escherichia coli.

Summary: The fission yeast Schizosaccharomyces pombe was grown in the presence of 10−3 to 10−6 m-sodium tellurite. Growth was inhibited by tellurite and at concentrations above 10−5 m a black reduction product (probably tellurium) was visible in sedimented cells. Electron microscopy of thin sections showed the reduction product to be on a localized system of membranous vesicles forming an area about 500 nm in diameter. Membrane systems of this type were not seen in control cells but they possibly resulted from the degeneration of some of the mitochondria.