The metabolic response of Saccharomyces cerevisiae to continuous heat stress.

A study has been initiated to integrate molecular and physiological responses of Saccharomyces cerevisiae to heat stress conditions. We focus our research on a quantification of the energetics of the stress response. A series of continuous heat stresses was applied to exponentially growing cells of the strain X2180-1A at 28 degrees C, by increasing the growth temperature to 37, 39, 40, 41, 42, or 43 degrees C. Here, the results on cell growth and viability, as well as on anabolic and catabolic rates are presented. We observed a surprisingly 'thin line' for the cells between growing, surviving, and dying, with regard to growth temperature. The heat stress showed a dual effect on catabolism: immediately after the temperature increase a strong peak was seen, after which a new, steady level was reached. In addition, the yield on glucose decreased with increasing temperature. Our results indicate that life at elevated temperatures is energetically unfavourable and a non-lethal heat stress invokes a redistribution of catabolic and anabolic fluxes.