Uncommon Glycerol Monoalkyl Glycerol Tetraethers (GMGT) Support Membrane Adaption in the Archaeon Pyrococcus Furiosus

Abstract

Summary Microbes preserve membrane functionality under fluctuating environmental conditions by modulating their membrane lipid composition, a strategy termed homeoviscous adaptation. Although several studies have documented this strategy in Archaea, the influence of the majority of biotic and abiotic factors on archaeal lipid compositions remains unexplored. To constrain the homeoviscous adaptation strategies in Archaea, we studied the influence of temperature, pH, salinity, elemental sulfur, carbon source, and genetic background on the remarkable core lipid composition of the hyperthermophilic and neutrophilic marine archaeon Pyrococcus furiosus. Most growth parameters tested here affected its core lipid composition, the carbon source and the genetic background having the greatest influences. Surprisingly, P. furiosus membrane adaptation appears to marginally rely on the two major homeoviscous responses implemented by Archaea, i.e., the regulation of the ratio between diethers and tetraethers and of the number of cyclopentane-rings in tetraethers. Instead, it increases the ratio of monoalkyl (GMGT) over dialkyl (GDGT) tetrathers in response to decreasing temperature and pH and increasing salinity. Besides P. furiosus, numerous other species synthesize significant proportions of GMGT, which indicates that this unprecedented homeoviscous strategy might be common in Archaea. This paves the way for developing novel, GMGT-based environmental proxies.