- Volume 128, Issue 2, 1982

Selenomonas ruminantium WPL 151/1 was grown in continuous culture anaerobically and at different gas phase partial pressures of oxygen (pO2). Low pO2 values led to substantial increases in whole-cell potential oxygen consumption rates and in NADH oxidase and superoxide dismutase activities in cell extracts. At the same time, concentrations of certain cytochrome pigments fell whilst lactate and acetate concentrations increased in the culture. As the pO2 was increased, growth yield became progressively lower, culture Eh became more positive and respiratory activity and NADH oxidase and superoxide dismutase activities fell. At these pO2 values cytochrome concentrations increased and fermentation products became more oxidized. Above a gas phase pO2 of 36·7 mmHg the culture began to wash out of the vessel. It is concluded that NADH oxidase and superoxide dismutase play an important part in protecting S. ruminantium against oxygen toxicity.

HeLa cells damaged by exposure to low pH released a diffusible attractant which greatly increased the collision frequency and hence the attachment of chemotactic Salmonella typhimurium. The attractant was tentatively identified as glycine. In contrast, when undamaged HeLa cells were used, no difference was found between a chemotactic parent strain and a non-chemotactic mutant in collision frequency or attachment. It is suggested that factors increasing cell membrane permeability could attract S. typhimurium to host cells in vivo.

Eight Staphylococcus xylosus strains lacking lytic activity (LA) were found to excrete agar-diffusible factors inhibiting the LA of LA-positive strains of the same species. The same eight strains, when tested against LA-positive indicator strains from other species of Micrococcaceae, caused marked LA inhibition only of strains of S. saprophyticus and S. cohnii, both species closely related to S. xylosus. Micrococci and planococci, unlike staphylococci, do not normally show LA, yet Micrococcus lylae and M. sedentarius strains produced inhibitors effective against the LA of almost all the indicator strains, and planococci inhibited the LA of a few indicator strains. Micrococcus luteus strains caused LA inhibition of homologous indicators only, i.e. exceptional M. luteus strains exhibiting LA. Thus, a specific and a non-specific type of LA inhibition can be distinguished, and it is suggested that the apparent lack of LA might, in some instances, be explained by the simultaneous production of a specific inhibitor.