LIPID-COMPOSITION OF A FREEZE-TOLERANT YEAST, TORULASPORA-DELBURECKII, AND ITS FREEZE SENSITIVE MUTANT

We analyzed the lipid compositions of a freeze-tolerant strain of yeas t Torulaspora delbrueckii D2-4 and its freeze-sensitive mutant 60B3 to clarify the relationship between the lipid composition and freeze tol erance of yeast. The total lipid content of D2-4 was similar to that o f 60B3, whereas the content of phospholipids and neutral lipids was di fferent from those of 60B3. The molar ratio of sterol to phospholipid in D2-4 was 60% of that in 60B3. The analysis of lipid components indi cated that D2-4 contained larger amounts of phosphatidylethanolamine, phosphatidylcholine, and phosphatidylinositol, but smaller amounts of triglyceride as compared to 60B3. These results suggest that the plasm a membrane of freeze-tolerant strain D2-4 may have a higher fluidity t han that of freeze-sensitive strain 60B3.