EFFECT OF 2,4-DINITROPHENOL ON THE RESISTANCE OF A TURBIDOSTAT YEAST CULTURE TO HEAT-SHOCK

The resistance of a turbidostat culture of Saccharomyces cerevisiae 14 to heat shock was investigated. The growth rate of the turbidostat cu lture after a cultivation temperature shift from a suboptimal (20 degr ees C) or optimal (30 degrees C) value to a supraoptimal value of 37.5 degrees C was taken as an index of heat-shock resistance. Experiments were performed in two variants: with 2,4-dinitrophenol (DNP) present in both the cells and medium and with DNP present only in the medium. Cells were found to be resistant to heat shock when they contained no DNP; intracellular DNP did not prevent the formation of the system res ponsible for thermotolerance, but hindered the functioning of this sys tem. The resistance of yeast to heat shock is presumably determined by the efficiency of oxidative phosphorylation.