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Effect of Temperature on the Fatty Acid Composition of Thermus aquaticus

Department of Biochemistry, University of Kentucky Medical Center, Lexington, Kentucky 40506
Department of Microbiology, University of Indiana, Bloomington, Indiana 47401

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.