Oxygen pressure, fatty acid composition and ergosterol level in Rhodotorula gracilis

Cells of Rhodotorula gracilis grown for 6 hrs at 2 mm Hg O2 pressure when compared with cells grown for 6 hrs at 140 mm Hg, show: a) a large decrease in the level of ergosterol, b) a significant increase in the level of oleic acid and a decrease in the levels of linoleic and linolenic acids, both in the fatty acid fraction of the phospholipids and in the free fatty acids and neutral fat fractions. The results suggest that the dehydrogenation of oleic acid to linoleic acid is preferentially inhibited at low O2 pressure. The possibility is considered that these changes of lipid metabolism might be causally related with decrease of the growth rate observed at low O2 pressure.