Conditioning by mitochondria and energy source of thermal death parameters in yeast

Two strains of Saccharomyces cerevisiae of opposite mating type (a and alpha), with different resistance to thermal death, and their respective mitochondrial respiratory-deficient mutants (petites ap and alpha p) were used to prepare the following diploid strains: a alpha, a alpha p and ap alpha. Specific thermal death rates were determined at supramaximum temperatures for growth, under conditions of mitochondrial derepression (glycerol medium). Comparison of the entropies of activation of thermal death showed that diploids a alpha and ap alpha behaved like the more resistant haploid alpha, and diploid a alpha p like haploid a. In glucose medium strains alpha and a alpha became even more thermoresistant. The results favour the concept that thermal death determinants are located in the mitochondrial genome, and that mitochondria repressed cells repair thermal injuries more efficiently.