Adaptation of the membrane in Archaea

- We present evidence that Archaea regulate membrane composition as a function of environmental stressors.
- Lipid composition variations are consistent with homeoviscous adaptation to maintain membrane functionality under stress.
- Specific modifications include the incorporation of cycles, unsaturation or modifying the ratio of di- to tetraether lipids.
- We highlight the limits of homeoviscous adaptation to interpret several specific membrane lipid compositions.
- These limits are attributed to imprecise lipid comopsition or poor understanding of the archael membrane structure.

Microbes often face contrasted and fluctuating environmental conditions, to which they need to adapt or die. Because membranes play a central role in regulating fluxes inward and outward from the cells, maintaining the appropriate structure of the membrane is crucial to maintain cellular integrity and functions. This is achieved in bacteria and eucarya by a modification of the membrane lipid compositions, a strategy termed homeoviscous adaptation. We review here evidence for homeoviscous adaptation in Archaea, and discuss the limits of this strategy and our knowledge in this very peculiar domain of life.