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Abstract
Populations of Saccharomyces cerevisiae NCYC 366, grown anaerobically under conditions that lead to enrichment of membranes with specific sterols and fatty-acyl residues, were subjected to freeze-thaw cycles and cold-shock stress. One freeze-thaw cycle caused considerable loss in viability, the loss being greater with organisms enriched in campesterol or cholesterol rather than ergosterol or stigmasterol. Retention of viability was greater in populations enriched in linoleyl rather than oleyl residues. Organisms enriched in ergosterol and either oleyl or cetoleyl residues were equally susceptible to death following freeze-thaw cycles, but less so than organisms enriched in palmitoleyl residues. Speed of freezing had little effect on retention of viability in organisms enriched in ergosterol and linoleyl residues, but an effect was observed in populations enriched in cholesterol and linoleyl residues. In populations enriched in ergosterol and linoleyl residues, sodium chloride protected against loss of viability, whereas in organisms enriched in cholesterol and linoleyl residues the salt rendered populations more susceptible to death following freezing and thawing. Resistance to cold-shock stress was also greater in populations enriched in ergosterol or stigmasterol rather than campesterol or cholesterol, and with organisms enriched in linoleyl rather than oleyl residues.
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