SYNOPSIS. A reduction in the growth temperature of Tetrahymena pyriformis strain WH‐14 from 35 C to 15 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 Δ6,11(n) and decreased in 18:2 Δ9,12(n) and 18:3 Δ6,9,12(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 γ‐linolenic acid [16:0(n) → 18:0(n) → 18:1 Δ9(n) → 18:2 Δ9,12(n) → 18:3 Δ6,9,12(n)] and an increase in the components of the pathway leading to the formation of 18:2 Δ6,11(n) [16:0(n) → 16:1 Δ9(n) → 18:1 Δ11(n) → 18:2 Δ6,11(n)]. The data suggest that the regulatory mechanism in Tetrahymena differs from that found in some bacteria where a simple substitution of unsaturated fatty acids for saturated fatty acids occurs at low culture temperatures.
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Conner et al. (1976) studied this question.
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