Fig. 2. des mRNA and UFA production in wild-type and yocG^– strains after a downshift temperature. (A) Northern blot analysis using formaldehyde agarose gels was carried out as described in Materials and methods. Total RNA was isolated from strains JH642 (lane 1) or strain AKP8 (yocG^–, lane 2) grown until mid-exponential phase at 37°C and then shifted to 25°C by 30 min. Each lane contains 10 µg of total RNA. (B) Fatty acids synthesized by strains JH642 and AKP8 at 25°C. Cultures of strains JH642 (lane 1) and AKP8 (lane 2) were grown to mid-exponential phase at 37°C, then 2 ml of these cultures were challenged with 10 µCi of [¹⁴C]acetate and further shifted to 25°C for 12 h. The lipids were then extracted and transesterified, and the resulting methyl esters were separated into saturated (SFAs) and unsaturated (UFAs) fractions by chromatography on 20% silver nitrate-impregnated silica gel thin-layers plates. The plates were developed at –17°C and autoradiographed by 7 days. The sample in lane 1 contained 15 000 c.p.m. and 2000 c.p.m. in the SFA and UFA fractions, respectively. The sample in lane 2 contained 14 000 c.p.m. in the SFA fraction, while the UFA fraction contained only background levels of radioactivity.