CONTROL OF CELL MORPHOLOGY OF THE YEAST SACCHAROMYCES-CEREVISIAE BY NUTRIENT LIMITATION IN CONTINUOUS-CULTURE

Saccharomyces cerevisiae IFO 0203, a polyploid yeast used in ethanol production in Japan, grows as ovoid cells in unstirred batch culture and on fully nutritive agar plates (2% w/v glucose; 0.67% w/v Difco yeast nitrogen base). Extensively branched pseudohyphae formed on 0.01% w/v ammonium sulphate plates within a few days. In continuous culture with high oxygen supply and limiting glucose, cells were elongated but growth was vigorous and the daughter cells separated well after budding. Limitation of growth by either nitrogen source or oxygen during continuous culture resulted in formation of truncated, occasionally branched, pseudohyphae up to five cells in length.