Membrane phospholipids in temperature adaptation of Candida utilis: alterations in fatty acid chain length and unsaturation.

The effect of decreasing environmental temperature on membrane phospholipids (PL), the neutral lipid (NL) composition, and their fatty acid profiles was studied in exponentially growing Candida utilis from 40 to 10 degrees C, at intervals of 5-9 centigrade degrees. According to the results, fatty acid unsaturation increased with decreasing growth temperature from 40 to 26-20 degrees C, due to the increase in PL containing the most unsaturated fatty acid, linolenic acid (mp. -11.3 to -12.8 degrees C). Concomitantly, an equal (phosphatidylcholine, PC; phosphatidylethanolamine, PE) or more pronounced (phosphatidylinositol and phosphatidylserine, PI + PS) decrease occurred in fatty acids with lower unsaturation and, consequently, the cellular fatty acid content decreased as the temperature was reduced from 40 to 26-20 degrees C. In addition, when the temperature decreased within the lower growth temperature range from 26-20 to 10 degrees C, the fatty acid chain length also shortened in PL, due to the increase in palmitoleic acid (mp. 0 degrees C), and equal (PC and PE) or more pronounced (PI + PS) decrease in other acids. Concomitantly, triacylglycerols accumulated as the temperature decreased from 26-20 to 10 degrees C. Thus, the results showed that C. utilis can adapt cellular membranes to decreases in the environmental temperature so that fatty acid unsaturation increases down to 26-20 degrees C, and t temperatures below that the fatty acid chain length also shortens.