Temperature regulation of membrane composition in the Firmicute, Enterococcus faecalis, parallels that of Escherichia coli

Both Enterococcus faecalis and Escherichia coli can undergo abrupt temperature transitions in nature. E. coli changes the composition of its phospholipid acyl chains in response to shifts growth temperature. This is mediated by a naturally temperature sensitive enzyme, FabF (3-ketoacyl-acyl carrier protein synthase II), that elongates the 16 carbon unsaturated acyl chain palmitoleate to the 18 carbon unsaturated acyl chain, cis-vaccenate. FabF is more active at low temperatures resulting in increased incorporation of cis-vaccenoyl acyl chains into the membrane phospholipids. This response to temperature is an intrinsic property of FabF and does not require increased synthesis of the enzyme. We report that the FabF of the very divergent bacterium, E. faecalis, has properties very similar to E. coli FabF and is responsible for changing E. faecalis membrane phospholipid acyl chain composition in response to temperature. Moreover, expression E. faecalis FabF in an E. coli ∆fabF strain restores temperature regulation to the E. coli strain.