Sphaeroplast Formation in Yeast During the Transition from Exponential Phase to Stationary Phase

SUMMARY: The sensitivity of Saccharomyces cerevisiae to sphaeroplast formation has been examined during the transition from the exponential phase of growth to the stationary phase. Exponential-phase yeasts are sensitive to sphaeroplast formation while stationary yeasts are resistant. During the transition period, there is a rapid increase in resistance to sphaeroplast formation. This increase can be inhibited by treatment with either cycloheximide or 5-fluorouracil. It is suggested that the resistance to sphaeroplast formation characteristic of stationary-phase yeasts is the result of a specific modification of the yeasts during the transition period which is dependent on both RNA and protein synthesis.