Relationship between lipid composition, frequency of ethanol-induced respiratory deficient mutants, and ethanol tolerance in Saccharomyces cerevisiae

The frequency of ethanol-induced respiratory deficient mutants and lipid co mposition in two Saccharomyces cerevisiae strains showing different degrees of ethanol tolerance were investigated. The more ethanol-tolerant strain e xhibited a lower frequency of ethanol-induced respiratory deficient mutants than the less ethanol-tolerant strain. In addition, the more ethanol-toler ant strain contained a higher ergosterol/ phospholipid ratio, a higher prop ortion of phosphatidylcholine, a lower proportion of phosphatidylethanolami ne, a higher incorporation of long-chain fatty acids in total phospholipids , and a slightly higher proportion of unsaturated fatty acids in total phos pholipids than the less ethanol-tolerant strain. These results show a clear relationship between the lipid composition, the frequency of ethanol-induc ed respiratory deficient mutants, and the ethanol tolerance of S. cerevisia e. A possible explanation of this relationship is discussed.