High membrane fluidity is related to NaCl stress in Candida membranefaciens

Abstract

The effect of hypersaline stress on the lipid composition of the salt-tolerant yeast Candida membranefaciens was studied. Fatty acid analyses of the plasma membrane showed a growth phase- and dose-dependent increase in the level of linolenic acid (C18:3) in 1.35 M NaCl-stressed cells. Palmitoleic acid (C16:1) was completely undetectable at all phases of the life cycle. Changes in the levels of other fatty acids were insignificant. The degree of unsaturation of fatty acids in the plasma membranes was higher in presence of 1.35 M NaCl. The fluorescence polarisation value of DPH (1,6-diphenyl- 1,3,5-hexatriene) in the spheroplasts of the stressed cells was lower as compared to the control cells, indicating the fact that a higher membrane fluidity favours osmotic adaptation against NaCl stress. Among different phospholipids, levels of Phosphatidylinositol and Phosphatidylethanolamine were elevated in the salt-adapted cells as compared to their controls. The levels of Phosphatidylcholine and cardiolipin did not change significantly in response to hypersaline stress. The study points out that hypersalinity signals affect the lipid composition which in turn affects the membrane fluidity of C. membranefaciens.