Effect of Temperature on the Fatty Acid Composition of Thermus aquaticus

Abstract

Thermus aquaticus contains four major fatty acids, iso-C₁₅ (28%), iso-C₁₆ (9%), normal-C₁₆ (13%), and iso-C₁₇ (48%), when grown at 70 C, as determined by gas chromatography and mass spectrometry. Small amounts of iso-C₁₂, normal-C_12:1, iso-C₁₃, normal-C₁₄, iso-C₁₄, and normal-C_15:1 were also detected. A change in growth temperature (50 to 75 C at 5-C intervals) affects a shift in the proportions of some of the fatty acids. The proportions of the monoenoic and branched-C₁₇ fatty acids decreased and the proportions of the higher-melting iso-C₁₆ and normal-C₁₆ fatty acids increased. Cells grown at 75 C contained 70% more total fatty acids than cells grown at 50 C. The largest increases, in absolute amounts, were in the content of iso-C₁₆ and normal-C₁₆ fatty acids, with only a 1.6-fold increase in the major iso-C₁₅ and iso-C₁₇ fatty acids. There was a 2.5-fold decrease in normal-C_15:1 and at least a 24-fold decrease in anteiso-C₁₇, which is present at 50 and 55 C but not at higher temperatures. There was no difference in proportion or amount of fatty acids between exponential and stationary-phase cells grown at 70 C. When cells were grown on glutamate instead of yeast-extract and tryptone at 70 C, the total fatty acid content remained constant, but there was an increase in the proportions of iso-C₁₆ and normal-C₁₆ fatty acids concomitant with a decrease in the proportions of the iso-C₁₅ and iso-C₁₇ fatty acids.