STATIONARY-PHASE IN THE YEAST SACCHAROMYCES-CEREVISIAE

Growth and proliferation of microorganisms such as the yeast Saccharom yces cerevisiae are controlled in part by the availability of nutrient s. When proliferating yeast cells exhaust available nutrients, they en ter a stationary phase characterized by cell cycle arrest and specific physiological, biochemical, and morphological changes. These changes include thickening of the cell wall, accumulation of reserve carbohydr ates, and acquisition of thermotolerance. Recent characterization of m utant cells that are conditionally defective only for the resumption o f proliferation from stationary phase provides evidence that stationar y phase is a unique developmental state. Strains with mutations affect ing entry into and survival during stationary phase have also been iso lated, and the mutations have been shown to affect at least seven diff erent cellular processes: (i) signal transduction, (ii) protein synthe sis, (iii) protein N-terminal acetylation, (iv) protein turnover, (v) protein secretion, (vi) membrane biosynthesis, and (vii) cell polarity . The exact nature of the relationship between these processes and sur vival during stationary phase remains to be elucidated. We propose tha t cell cycle arrest coordinated with the ability to remain viable in t he absence of additional nutrients provides a good operational definit ion of starvation-induced stationary phase.