RELATIONSHIP BETWEEN CADMIUM SENSITIVITY AND DEGREE OF PLASMA-MEMBRANE FATTY-ACID UNSATURATION IN SACCHAROMYCES-CEREVISIAE

The sensitivity of Saccharomyces cerevisiae to the redox-active metal copper has recently been found to be influenced by cellular fatty acid composition. This study sought to investigate whether fatty acid comp osition affected plasma membrane permeabilisation and whole-cell toxic ity induced by the redox-inactive metal cadmium. S. cerevisiae NCYC 13 83 was enriched with the polyunsaturated fatty acids linoleate (18:2) and linolenate (18:3) by growth in 18:2- or 18:3-supplemented medium. Incorporation of the exogenous fatty acids resulted in them comprising more than 65% of the total fatty acids in plasma membrane lipids. Inh ibition of cell division in the presence of Cd(NO3)(2) was accentuated by growth in the presence of a polyunsaturated fatty acid. Furthermor e, susceptibility to Cd2+-induced plasma membrane permeabilisation inc reased with the degree of fatty acid unsaturation. Thus, during exposu re to Cd2+, K+ efflux from 18:2- and 18:3-enriched cells was up to 2.5 -fold or 3-fold greater, respectively than that from unsupplemented ce lls. In addition, reductions in cell viability during exposure to Cd2 were most marked in polyunsaturated-fatty-acid-supplemented cells. At certain times, unsupplemented Cd2+-exposed cells displayed up to 7-fo ld greater viability than supplemented Cd2+-exposed cells. The study d emonstrates that the toxicity of the redox-inactive metal Cd2+ towards S. cerevisiae becomes markedly amplified with increased cellular and plasma membrane fatty acid unsaturation.