Regulation of membrane lipid homeostasis in bacteria upon temperature change

Abstract

Bacteria precisely remodel the fluidity oftheir membrane bilayer via the incorporation of proportionally more unsaturatedfatty acids (or fatty acids with analogous properties, such as branched-chainfatty acids) as growth temperature decreases. This process, termed homeoviscousadaptation, is suited to disrupt the order of the lipid bilayer andoptimizes the performance of a large array of cellular physiological processesat the new temperature. As such, microbes have developed molecular strategiesto sense changes in membrane fluidity, provoked by a decrease in environmentaltemperature, and initiate cellular responses that upregulate the biosynthesisof either unsaturated, terminally branched or shorter chain fatty acids. In this review wedescribe some of the basic molecular strategies that bacteria use to sensetemperature. While the activities of all biomolecules are altered as a function oftemperature, the thermosensors we focus on here are molecules whose temperaturesensitivity provides information about the thermal environment that is used totrigger an appropriate adjustment of membrane architecture. We also discussselected examples of membrane and lipopolysaccharide remodeling induced bycold, that involves changes in the activity of fatty acid biosynthetic enzymesor the expression of acyltransferases that modify the lipid A.