The Effect of Temperature on the Fatty Acid Composition of Tetrahymena pyriformis WH‐14

Abstract

A reduction in the growth temperature of T. pyriformis strain WH-14 from 35.degree. C to 15.degree. C resulted in distinct alterations in the fatty acid composition of the glycerophospholipids. The proportion of normal saturated acids declined from 26 to 19%; palmitoleic acid increased by 6%, and the composition of the polyunsaturated fatty acids increased in 18:2 .DELTA.6,11 (n) and decreased in 18:2 .DELTA.9,12 (n) and 18:3 .DELTA.6,9,12 (n). The unsaturation index (the average number of double bonds/100 molecules) did not change with a shift in temperature. Two biosynthetic pathways exist in Tetrahymena for the formation of unsaturated fatty acids. The observed changes in fatty acid composition that accompany a lowering of the environmental temperature can be accounted for by a reduction in the accumulation of products of the fatty acid pathway leading to the formation of .gamma.-linolenic acid [16:0 (n) .fwdarw. 18:0 (n) .fwdarw. 18:1 .DELTA.9 (n) .fwdarw. 18:2 .DELTA.9,12 (n) .fwdarw. 18:3 .DELTA.6,9,12 (n)] and an increase in the components of the pathway leading to the formation of 18:2 .DELTA.6,11 (n) [16:0 (n) .fwdarw. 16:1 .DELTA.9 (n) .fwdarw. 18:1 .DELTA.11 (n) .fwdarw. 18:2 .DELTA.6,11 (n)]. The regulatory mechanism in Tetrahymena seems to differ from that found in some bacteria where a simple substitution of unsaturated fatty acids for saturated fatty acids occurs at low culture temperatures.