HIGH MEMBRANE FLUIDITY IS RELATED TO NACL STRESS IN CANDIDA-MEMBRANEFACIENS

The effect of hypersaline stress on the lipid composition of the salt- tolerant yeast Candida membranefaciens was studied. Fatty acid analyse s of the plasma membrane showed a growth phase- and dose-dependent inc rease in the level of linolenic acid (C-18:3) in 1.35 M NaCl-stressed cells. palmitoleic acid (C-16:1) was completely undetectable at all ph ases of the life cycle. Changes in the levels of other fatty acids wer e insignificant The degree of unsaturation of fatty acids in the plasm a membranes was higher in presence of 1.35 M NaCl. The fluorescence po larisation value of DPH (1,6-diphenyi- 1,3,5-hexatriene) in the sphero plasts of the stressed cells was lower as compared to the control cell s, 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 the controls. The levels of Pho sphatidylcholine and cardiolipin did not change significantly in respo nse to hypersaline stress. The study points out that hypersalinity sig nals affect the lipid composition which in turn affects the membrane f luidity of C. membranefaciens.