- Volume 115, Issue 1, 1979

Growth efficiency (c) and specific maintenance rate constant (μ e) were determined in continuous cultures of the cyanobacterium Oscillatoria agardhii Gomont, in light energy-limiting conditions, according to the formula μ = cq E-μ e in which q E is the specific light energy uptake rate. Values of the efficiency factor c varied with irradiance from 0·23 at 0·5 W m−2 to 0·05 at 40 W m−2. The specific maintenance rate constant was 0·001 h−1. The culture pH value influenced c and μ e . A diurnal light/dark cycle with a 16 h photoperiod did not affect either of the two parameters, μ e and c. The relationship between growth rate and light energy uptake rate, embodied in the above formula, was also valid for nitrogen (nitrate)-limited cultures.

Many sugars and derivatives were tested in the capillary assay for their attraction of Bacillus subtilis. The major attractants were 2-deoxy-d-glucose, d-fructose, gentiobiose, d-glucose, maltose, d-mannitol, d-mannose, N-acetylglucosamine, α-methyl-d-glucoside, β-methyl-d-glucoside, N-acetylmannosamine, α-methyl-d-mannoside, d-sorbitol, l-sorbose, sucrose, trehalose and d-xylose. Only glucose chemotaxis was completely constitutive. Competition experiments were carried out to determine the specificities of chemoreceptors. There were 25 instances of no influence of two sugars on each other’s taxis, 92 instances of one sugar interfering non-reciprocally with chemotaxis towards another and 49 instances of two sugars reciprocally competing. However, in most of the last instances, other sugars were identified that interfered with chemotaxis towards one member of the pair but not the other. Thus, nearly all sugars and related compounds appear to be detected by their own chemoreceptors, but many secondary interactions exist.

Alcaligenes eutrophus strain H16 when grown on formate or oxalate as the sole source of carbon and energy had doubling times between 3·5 and 4·5 h. The respective molar growth yields (Y m) were 2·35 and 3·9. During growth on formate or oxalate both a soluble and a membrane-bound formate dehydrogenase were formed. The key enzymes of autotrophic CO2 fixation, ribulose-5-phosphate kinase and ribulosebisphosphate carboxylase, were formed during growth on formate but not on oxalate. Oxalate induced the synthesis of the enzymes of the glycerate pathway. Mutants impaired in autotrophic CO2 fixation but unaffected in the synthesis of the formate dehydrogenases lost their ability to grow on formate but not to grow on oxalate, giving further evidence that formate was assimilated via CO2.

The inhibitory effect of l-lysine on penicillin biosynthesis by Penicillium chrysogenum has been compared in a low-producing strain (Wis. 54–1255) and a high-producing strain (AS-P-78). Lysine inhibited total penicillin synthesis to a similar extent in both strains. However, in the high-producing strain the onset of penicillin synthesis occurred even at a high lysine concentration, whereas in the low-producing strain lysine had to be depleted before penicillin production commenced.

Linoleic acid, but not stearic acid, inhibited the growth of Staphylococcus aureus NCTC 8325. Growth inhibition was associated with an increase in the permeability of the bacterial membrane. The presence of a plasmid conferring resistance to penicillin (PC plasmid, e.g. pI258 blaI−) increased the growth inhibitory and membrane permeability effects of linoleic acid. Under growth inhibitory conditions, linoleic acid was incorporated into the lipid of both PC plasmid-containing and PC plasmid-negative bacteria and there was little difference between these cultures in the uptake or fate of linoleic acid. Experiments using a glycerol auxotroph of S. aureus suggested that free linoleic acid, rather than lipid containing this acid, inhibits growth. Linoleic acid probably inhibits growth by increasing the permeability of the bacterial membrane as a result of its surfactant action, and the presence of the PC plasmid increases these effects.

Ten species of fungi were obtained from poultry droppings in Nigeria. Six of these are true thermophiles while the other four are thermotolerant. Aspergillus fumigatus Fresenius, Mucor pusillus Lindt and Thermoascus aurantiacus Stolk are known human pathogens. Except for M. pusillus, all the thermotolerant species had a higher occurrence at 45°C while the thermophilic varieties were readily obtained at 50°C.

Spores of the fission yeast Schizosaccharomyces pombe have been separated from vegetative cells by a simple and rapid centrifugation (800 g for 20 min) through a 35% Hypaque solution to a purity >95%. Approximately 35% of the spores were recovered. Regrowth in EMM2 plus glucose showed that over 97% of the spores germinated within the first 2 h and outgrowth continued between 5 and 10 h. Sucrose induced germination in > 95% of the spores with a 1 h delay and outgrowth in 50 % of the spores with a 3 h delay. There was little protein synthesis during germination but the protein content increased linearly coincident with outgrowth. The RNA content increased slightly during germination, but increased linearly 1 h before the onset of outgrowth and protein synthesis. After 8 h of regrowth, coincident with the onset of DNA synthesis, the rate of RNA synthesis was accelerated. The DNA content had increased 1·7-fold after 10 h of regrowth from a haploid level of 1·36 10−8 μg spore−1.