Asymmetrical Division of Saccharomyces cerevisiae in Glucose-limited Chemostat Culture

Saccharomyces cerevisiae S288C/1 was grown in a glucose-limited chemostat at population doubling times (τ) of 80 to 736 min. Estimates of the daughter cycle time (D), the parent cycle time (P) and the budded period (B) were obtained from bud scar analyses and equations derived from the Hartwell & Unger model of asymmetric cell division. D, P and B all showed biphasic linear relationships to τ, quantitatively different from estimates for the same strain in batch culture. Median cell volume and dry weight per cell increased at the faster growth rates, but the average cell density reached a minimum at τ = 150 min. The contiguous array of bud scars on parent cells became increasingly irregular as the doubling time increased from 140 min. At the fastest growth rates a small percentage of filamentous forms were observed due to failure of cells to undergo cell separation.