Adaptive Regulation of Membrane Lipid Biosynthesis in Bacilli by Environmental Temperature

Abstract

Some years ago, when we decided to study lipid metabolism in bacilli, we did so with several objectives in mind. One goal was to determine the mechanisms by which bacilli adaptively adjust the composition of their membrane lipids in response to changes in environmental temperature. We found that temperature-mediated variations in bacilli membrane lipids could be conveniently divided into slow, long-term alterations that required growth and net lipid synthesis, and short-term alterations that were rapidly implemented in response to temperature changes and did not necessarily involve new lipid synthesis. Slow alterations included shifts in fatty acid chain length and branching, increases in saturated to unsaturated fatty acids ratios, and changes in phospholipids head-group distribution. Fast alterations included changes in the asymmetrical distribution of phospholipid types on the two sides of the membrane bilayer and decreases in the ratios of saturated to unsaturated fatty acids in these lipids.