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

Two strains of Saccharomyces cerevisiae of opposite mating type ( a and α), with different resistance to thermal death, and their respective mitochondrial respiratory‐deficient mutants (petites a p and α p ) were used to prepare the following diploid strains: a α, a α p and a p α. 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 α and a p α behaved like the more resistant haploid α, and diploid a α p like haploid a. In glucose medium strains α and a α 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.