Effects of the temperature range and the lack of beta-ketoacyl acyl-carrier protein synthase II on fatty acid synthesis in Escherichia coli K12 after shifts in temperature.

Escherichia coli K12 cells grown at higher temperatures and then subjected to lower temperatures produce fatty acids with higher unsaturated/saturated ratios than cells completely adapted to the lower temperatures (Okuyama et al. (1982) J. Biol. Chem. 257, 4812-4817). This hyper-response was not an artefact of chloramphenicol treatment and was observed when the shift-down was more than 20 degrees C in the cells grown at either 40 degrees C or 35 degrees C. In contrast, cells grown at either 25 degrees C or 30 degrees C showed no appreciable hyper-response in terms of unsaturated/saturated ratio on temperature shifts to as low as 10 degrees C. By combining shift-down and shift-up experiments, we could show the presence of different types of temperature dependency in the fatty acid-synthesizing systems of cells grown at various temperatures. Contrary to wild-type cells which synthesized mainly cis-vaccenate on down-shift to 10 degrees C, a mutant strain lacking beta-ketoacyl acyl-carrier protein synthase II synthesized more palmitoleate (16:1) and less palmitate at 10 degrees C than at 40 degrees C. The average chain lengths of saturated and unsaturated fatty acids also changed, but differently, between the mutant and wild-type cells on shifts of temperature. Thus, the mutant strain has a temperature-dependent fatty acid-synthesizing system qualitatively different from that seen in a wild-type strain.