RELATIONSHIP BETWEEN ETHANOL TOLERANCE, LIPID-COMPOSITION AND PLASMA-MEMBRANE FLUIDITY IN SACCHAROMYCES-CEREVISIAE AND KLOECKERA-APICULATA

The lipid composition of a strain of each of two yeasts, Saccharomyces cerevisiae and Kloeckera apiculata, with different ethanol tolerances , was determined for cells grown with or without added ethanol. An inc rease in the proportion of ergosterol, unsaturated fatty acid levels a nd the maintenance of phospholipid biosynthesis seemed to be responsib le for ethanol tolerance. The association of ethanol tolerance of yeas t cells with plasma membrane fluidity, measured by fluorescence anisot ropy, is discussed. We propose that an increase in plasma membrane flu idity may be correlated with a decrease in the sterol:phospholipid and sterol:protein ratios and an increase in unsaturation index.