FIG. 7.

Fatty acids synthesized by strain AKP5 at 37 and 20°C. Cultures of strain AKP5 (lanes 1 to 4) were grown to mid-exponential phase at 37°C. One half of this culture was supplemented with 1 mM of IPTG. Two milliliters of treated (+) and untreated (−) cultures was challenged with 10 μCi of [¹⁴C]acetate and further shifted to 20°C (lanes 1 and 2) or maintained at 37°C (lanes 3 and 4) for 12 h. The lipids were then extracted and transesterified, and the resulting methyl esters were separated into saturated fatty acid (SFA) and UFA fractions by chromatography on 20% silver nitrate impregnated silica gel thin-layer plates. The plates were developed at −17°C and autoradiographed for 5 days. The UFA synthesized by strain JH642 grown at 37°C and then shifted to 20°C in the presence of 10 μCi of [¹⁴C]acetate for 12 h is shown in lane 5. The samples in lanes 1 and 3 contained 11,000 cpm in the SFA fractions, while the UFA fractions contained only background levels of radioactivity. The samples in lanes 2 and 4 contained 10,000 and 1,300 cpm of radioactivity in the SFA and UFA fractions, respectively. The sample in lane 5 contained 9,000 and 1,350 cpm of radioactivity in the SFA and UFA fractions, respectively.