Induction of rho- mutations in yeast Saccharomyces cerevisiae by ethanol

The kinetics of the killing effect of ethanol was studied at 6-30% concentrations. Ploidy of cells, deficiency of the excision-repair system or holding under no-growth conditions did not influence survival. Ethanol at 24% increased, in the wild strain, the number of respiration-deficient cells from a spontaneous level of 0.4% up to nearly half of all survivors. Genetic analysis showed the mitochondrial nature of induced respiration-deficient mutants (or rho-). The influence of yeast resistance to some antibiotics was studied on rho- mutagenesis, both spontaneous and induced by ethanol. Neomycin-resistant strains were characterized by a significantly lower level of these mutations than were neomycin-sensitive strains.