Ultradian metabolic oscillation of Saccharomyces cerevisiae during aerobiccontinuous culture: hydrogen sulphide, a population synchronizer, isproduced by sulphite reductase

摘要

We have reported that the consecutive cyclic production of H2S resulted in population synchrony of ultradian metabolic oscillation (Sohn ct ctl., 2000), In order to understand the origin of H2S and its nature of periodic production, changes of sulphur compounds concentration and responsible enzymes were investigated. The concentrations of extracellular sulphate, intracellular glutathione and cysteine oscillated during metabolic oscillation but only the oscillation of sulphate concentration was out of phase with H2S production. The sulphate concentration in culture directly affected the amplitude and the period of metabolic oscillation: (a) the period of metabolic oscillation shortened from 50 min to 30 min when sulphate concentration in the medium was reduced from 46 mM to 2.5 mM; (8) the metabolic oscillation disappeared under sulphate-depletion conditions and arose again by the addition of sulphate. Pulse injection of sulphite (10 muM) perturbed metabolic oscillation with a burst production of H2S, while thiosulphate (up to 500 muM) was without apparent effect. Furthermore, addition of S-adenosyl methionine (100 muM) or azoxybacilin (3 mg/kg) decreased H2S production with perturbation of metabolic oscillation. The results presented here suggest that H2S, a population synchronizer, is produced by sulphite reductase in the sulphate assimilation pathway, and dynamic regulation of sulphate uptake plays an important role in ultradian metabolic oscillation.