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Appl. Environ. Microbiol., Aug 1997, 2971-2976, Vol 63, No. 8
NG Howlett and SV Avery
The degree of plasma membrane fatty acid unsaturation and the copper
sensitivity of Saccharomyces cerevisiae are closely correlated. Our
objective was to determine whether these effects could be accounted for by
differential metal induction of lipid peroxidation. S. cerevisiae S150-2B
was enriched with the polyunsaturated fatty acids (PUFAs) linoleate (18:2)
and linolenate (18:3) by growth in 18:2- or 18:3- supplemented medium.
Potassium efflux and colony count data indicated that sensitivity to both
copper (redox active) and cadmium (redox inactive) was increased in
18:2-supplemented cells and particularly in 18:3-supplemented cells.
Copper- and cadmium-induced lipid peroxidation was rapid and associated
with a decline in plasma membrane lipid order, detected by fluorescence
depolarization measurements with the membrane probe trimethylammonium
diphenylhexatriene. Levels of thiobarbituric acid-reactive substances
(lipid peroxidation products) were up to twofold higher in
18:2-supplemented cells than in unsupplemented cells following metal
addition, although this difference was reduced with prolonged incubation up
to 3 h. Conjugated-diene levels in metal- exposed cells also increased with
both the concentration of copper or cadmium and the degree of cellular
fatty acid unsaturation; maximal levels were evident in 18:3-supplemented
cells. The results demonstrate heavy metal-induced lipid peroxidation in a
microorganism for the first time and indicate that the metal sensitivity of
PUFA-enriched S. cerevisiae may be attributable to elevated levels of lipid
peroxidation in these cells.
Copyright © 1997, American Society for Microbiology
Induction of lipid peroxidation during heavy metal stress in Saccharomyces cerevisiae and influence of plasma membrane fatty acid unsaturation
School of Biological and Molecular Sciences, Oxford Brookes University.
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