Stress resistance of yeast cells is largely independent of cell cycle phase.

Rapidly growing cells of Saccharomyces cerevisiae are sensitive to heat shock, while non-growing stationary phase cells are highly resistant. We find that slowly growing cells have an intermediate degree of heat shock resistance that can be nearly as great as that of stationary phase cells. This resistance is correlated both with slow growth and with carbon catabolite derepression. Slowly growing cells also showed resistance to Zymolyase digestion of their cell walls. The stress resistance is a property of all the cells in the culture, and cell cycle position makes little difference to the degree of stress resistance. At least some of the properties normally associated with stationary phase cells do not require residence in stationary phase or any other particular compartment of the cell cycle. Stress resistance may be due to a diverse set of physiological adaptations available to cells regardless of their position in the cell cycle. That is, although stress resistance and stationary phase are often correlated, neither is the cause of the other.