Changes in membrane lipid composition during temperature adaptation by a thermotolerant strain of Tetrahymena pyriformis.

Experiments on temperature adaptation have been conducted using a thermotolerant clone of Tetrahymena pyriformis designated as strain NT-1. The strain was able to grow well at 39.5 and 15 degrees C and could adapt quickly when transferred from one of these temperatures to the other. Cells grown at the extreme temperatures differed markedly in their membrane lipid composition, particularly in the phospholipid polar head groups and hydrocarbon chains. The levels of fatty acid unsaturation increased at the lower temperature (e.g. 15 degrees C cells contained 31% gamma-linolenic acid vs. 25% at 39.5 degrees C) as did the content of alkyl glyceryl ether derivatives. Ethanolamine phosphoglycerides decreased by more than 10 mol % of the lipid phosphorus with the drop in temperature, the decrease being offset by a concomitant rise in 2-aminoethylphosphonolipid. These temperature-induced changes were noted in certain purified membrane preparations as well as in whole cells. Experiments with [14C]palmitic acid and sodium[14C]acetate showed that fatty acids are first incorporated into phospholipids predominantly in a saturated form. The membranes served as a reservoir of fatty acid substrate for desaturase activity. Tetrahymena pyriformis, strain NT-1, was proposed as a useful model system for studying the temperature adaptation process in eukaryotic cells.