- Volume 126, Issue 2, 1981

The synthesis of 1,3-β-glucanase, β-N-acetylglucosaminidase and total protein was studied during autolysis of Neurospora crassa. Evidence for de novo protein synthesis during autolysis was obtained from the incorporation of [3H]tryptophan and [3H]phenylalanine into the protein pool and from the inhibitory effects of cycloheximide and puromycin. Glucose accumulated in the growth medium during autolysis and N-acetylglucosamine and two unidentified oligosaccharides were detected towards the end of the 46 d autolysis period. During autolysis, 1,3-β-glucanase accumulated in the medium to tenfold greater activities than β-N-acetylglucosaminidase. The former enzyme had a pH optimum of 5·5; and a K m of 0·45 mm. It was inhibited by excess substrate but not by excess glucose.

The cyanobacterium Oscillatoria agardhii Gomont was grown in continuous culture under nitrate- or light-limited conditions. Short-term uptake rates of nitrate and ammonium were studied at various concentrations of nitrate and ammonium, both of which were present during the short-term assay. In nitrate-limited O. agardhii, the short-term ammonium uptake rate was not influenced by the presence of nitrate. Ammonium inhibited the rate of nitrate uptake in a non-competitive manner. An equation was derived for the short-term nitrate uptake rate which was a function of the ambient concentrations of both nitrate and ammonium. For a low ammonium concentration tested, the pattern of the nitrate-ammonium interaction in light-limited O. agardhii did not differ greatly from that found in nitrate-limited O. agardhii.

Fungicides inhibiting sterol biosynthesis belong to chemically distinct classes such as imidazole, morpholine, pyridine, pyrimidine and triazole derivatives. Incubation of mycelium of Aspergillus nidulans for 90 min with representatives of these fungicides induced an efflux activity which prevented accumulation of fenarimol, a pyrimidine derivative, into the mycelium. Induction of this efflux activity reduced the fungitoxicity of fenarimol. Addition of oligomycin to mycelium in which fenarimol-efflux activity was induced immediately increased the uptake of fenarimol, indicating that the efflux activity is energy-dependent. Subsequent disruption of membrane permeability with sodium lauryl sulphate instantaneously caused leakage of fenarimol from the mycelium into the medium. The ability to induce fenarimol efflux is rather specific for inhibitors of sterol biosynthesis: except for pimaricin, fungicides with unrelated mechanisms of action did not have this ability.

Nitrofurantoin causes the stringent response in Bacillus subtilis. After exposure of a stringent strain to this drug, the intracellular concentrations of guanosine 3′-diphosphate 5′-diphosphate (ppGpp), guanosine 3′-diphosphate 5′-triphosphate (pppGpp) and ATP increased, while that of GTP decreased. In a relaxed strain no accumulation of ppGpp or pppGpp was observed, but both GTP and ATP declined after the addition of nitrofurantoin. Protein synthesis was equally sensitive to nitrofurantoin in both the stringent and relaxed strains, but the drug inhibited RNA accumulation only in the stringent strain, not in the relaxed strain. Nitrofurantoin also caused the accumulation of ppGpp in Escherichia coli and Serratia marcescens.

Electron micrographs are shown of the gas-vacuolate square bacterium found at the surface of a brine pool in Sinai. The bacteria have a thickness of 0·1; μm or even less in the central regions. Some are apparently surrounded by sheath material. They contain gas vesicles which are either spindle-shaped or cylindrical with conical ends, and up to 1 μm long. The bacterial surface has 20 nm subunits arranged in a regular array.

One hundred and fifty-three isolates of coagulase-negative staphylococci obtained from human skin failed to transfer resistance to either cadmium ions (46 isolates), trimethoprim (37 isolates), erythromycin (25 isolates) or tetracycline (45 isolates) to Staphylococcus aureus strain 1030 or to each of 10 of its lysogenic derivatives in mixed cultures. Thirty-three trimethoprim-resistant coagulase-negative staphylococcal isolates obtained from the human intestine also failed to transfer this resistance to the recipients in mixed cultures.

A plasmid, pIJ2000, of approximately 7#x00B7;8 kilobase pairs (kb) and with a base composition of 22·4 mol% (G + C) has been isolated from the non-helical Spiroplasma citri strain ASP-1. pIJ2000 was the only covalently-closed circular DNA molecule detected in cleared ly sates of high passage cultures of strain ASP-1 following CsCl/ethidium bromide equilibrium buoyant density centrifugation. A primary isolate of strain ASP- 1 contained two additional plasmids of approximately 35#x00B7;4 kb and 14#x00B7;8 kb. pIJ2000 contained single sites for the restriction endonucleases BgZlII, HaeIII, HindIII and XhoI arid three sites for MboI.

Glutamate synthase (GOGAT) activities of the symbiotic cyanobacteria of the lichens Peltigera canina and Peltigera aphthosa and of the water fern Azolla caroliniana have been determined and, like glutamine synthetase (GS) activity, found to be substantially reduced compared with the activities found in the free-living cyanobacteria. A similar reduction in GOGAT activity was not noted in the symbiotic green alga (Coccomyxa sp.) in P. aphthosa. The selective reduction of GS-GOGAT activity in symbiosis may be related to the production of extracellular nitrogen by the symbiotic cyanobacterium.

Incorporation of activated charcoal into the agar enhanced the accuracy of phototaxis by Dictyostelium discoideum slugs two- or threefold. This was due to absorption of stray light rather than adsorption of a phototaxis-impairing chemical. The presence of charcoal had no effect on thermotaxis, the critical cell density at which phototaxis and thermotaxis become impaired, Slug Turning Factor (STF) interference with phototaxis, or chemotaxis by slugs in STF gradients. Activated charcoal in the agar had other effects on D. discoideum which may be chemical in nature.