THE METABOLISM OF YEAST SPORULATION: I. EFFECT OF CERTAIN METABOLITES AND INHIBITORS

Abstract

Cells of bakers' yeast harvested from a chemically-defined medium were placed in buffer for sporulation experiments and in Wickerham's yeast nitrogen base for growth experiments. The metabolites were included in these two solutions in concentrations up to 1% usually, and growth and sporulation were compared under conditions as nearly equivalent as possible. Optimum sporulation was observed in 0.033–0.1% glucose, 1% pyruvate, 0.033% ethanol, 0.033% acetaldehyde, and 0.33% acetate. Optimum growth in one day occurred in 1% glucose, 1% pyruvate, 0.1–0.33% ethanol, 0.0033% acetaldehyde, and 0.033% acetate. Very few asci were found in 0.33% glucose or in 1% ethanol, but cells transferred to buffer after one day in such solutions sporulated well. The addition of 0.33% glucose or 1% ethanol to 0.3% acetate suppressed sporulation. In 0.1% acetaldehyde no sporulation or growth was evident, with or without the addition of 0.3% acetate. Acetoin, 2,3-butylene glycol, and ethylene glycol had no marked effect on sporulation and growth. Sporulation and growth were inhibited by 7 × 10−4M fluoroacetate with 0.3% acetate or 0.3% ethanol as the carbon source. Inhibition was much greater when the acetate concentration was decreased to 0.03%. Sporulation in glucose was inhibited by fluoroacetate, while growth in glucose was little affected. With acetate as the carbon source, sporulation was more sensitive than growth to urethane, while the reverse was found with azide, malachite green, cyanide, and dinitrophenol. The two processes seemed about equally sensitive to arsenite, p-nitrophenol, and malonic acid. Most of the asci that formed in glucose solutions were two-spored. In acetate, ethanol, and pyruvate three- and four-spored asci usually predominated, except in the weaker concentrations.