NO+, but not NO., inhibits respiratory oscillations in ethanol-grown chemostat cultures of Saccharomyces cerevisiae.

A continuous culture of Saccharomyces cerevisiae strain IFO 0233 growing aerobically at pH 3.4 shows persistent high-amplitude respiratory oscillations with a period of about 45 min. These robust autonomous cycles are accompanied by changes of product accumulation (acetaldehyde and acetic acid), intracellular pH, and intracellular redox state, as indicated by continuously monitored NADH fluorescence and the glutathione content of cell-free extracts. Perturbation of the oscillation of dissolved O2 was produced on addition of 100 microM glutathione, > 10 nM Na nitroprusside, 8 microM NaNO2, or 10 microM S-nitrosoglutathione. NO gas, putative NO.-releasing agents, or an inhibitor of NO synthase were ineffective. We suggest that nitrosation by NO+ of a component of a redox switch can account for these data, and we emphasise the different modes of action of the different redox forms of nitrogen monoxide.