Role of mitochondria in ethanol tolerance of Saccharomyces cerevisiae.

The presence of active mitochondria and oxidative metabolism is shown to be essential to maintain low inhibition levels by ethanol of the growth rate (mu), fermentation rate (nu) or respiration rate (rho) of Saccharomyces cerevisiae wild type strain S288C. Cells which have respiratory metabolism show Ki (ethanol inhibition constant) values for mu, nu and rho, higher (Ki greater than 1 M) than those of "petite" mutants or "grande" strains grown in anaerobiosis (Ki = 0.7 M). In addition, the relationship between mu or nu and ethanol concentration is linear in cells with respiratory metabolism and exponential in cells lacking respiration. When functional mitochondria are transferred to "petite" mutants, the resulting strain shows Ki values similar to those of the "grande" strain and the inhibition of mu and nu by increasing ethanol concentrations becomes linear.