Minimal requirements for membrane adaptation of the bacterial model organism M. extorquens

Cells, from microbes to man, adapt their membranes in response to the environment to maintain functionality. How cells sense environmental change/stimuli and adapt their membrane accordingly is unclear. In particular, how lipid composition changes and what lipid structural features are necessary for homeostatic adaptation remains relatively undefined. Here, we examine the simple yet adaptive lipidome of the plant-associated Gram-negative bacterium Methylobacterium extorquens over a range of chemical and physical conditions. Using shotgun lipidomics, we explored adaptivity over varying temperature, hyperosmotic and detergent stress, carbon sources, and cell density. Globally, we observed that as few as 10 lipids, representing ca. 30% of the lipidome, characterized by 9 structural features account for 90% of the total changes. We revealed that variations in lipid structural features are not monotonic over a given range of conditions (e.g. temperature) and are not evenly distributed across lipid classes. Thus, despite the compositional simplicity of this lipidome, the patterns in lipidomic remodeling suggest a highly adaptive mechanism with many degrees of freedom. Our observations reveal constraints on the minimal lipidomic requirements for an adaptive membrane and provide a resource for unraveling the design principles of living membranes.