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Abstract
SUMMARY: Saccharomyces cerevisiae NCYC 366 was grown anaerobically under conditions that induce a requirement for a sterol and an unsaturated fatty acid. In media containing ergosterol and either oleic acid, linoleic or γ-linolenic acid, organisms grew at about the same rate, although the duration of the lag phase of growth was extended as the degree of unsaturation in the exogenous fatty acid was increased. Organisms grown in each of the three media did not differ in their contents of total lipids or total phospholipids. Between 54 and 65% of the fatty-acid residues in lipids extracted from organisms were the same as the fatty acid supplied in the medium. Organisms grown in linoleic acid-containing medium were less susceptible to sphaeroplast formation, by digestion of the wall with a basidiomycete glucanase, than were organisms grown in the presence of oleic acid. Sphaeroplasts could be obtained from organisms grown in the presence of linolenic acid if spermine was included in the glucanase digest. Sphaeroplasts formed in the presence of spermine from organisms grown in oleic acid-containing medium were less susceptible to osmotic lysis than sphaeroplasts formed from these organisms in the absence of spermine. The effect of spermine was less pronounced with organisms grown in media containing linoleic acid. The inclusion of spermine in the hypotonic solutions of sorbitol did not affect the kinetics of lysis of sphaeroplasts from organisms grown in medium containing oleic acid or linoleic acid.
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