Molecular dynamics simulations reveal methylation in Me-GDGTs as a microbial low-temperature adaptation

Tetraether membrane lipid glycerol dialkyl glycerol tetraether (GDGT) is a characteristic lipid of archaea that contributes to adaptation to a variety of environments and has been widely used in ecological and geochemical studies. Alkyl-chain methyl-modified GDGTs (Me-GDGTs) as one important component have been detected in both environmental and culture samples. However, the effect of methyl modification on archaeal membrane lipids remains unclear, hampering the development of environmental proxies based on the exact understanding of the underlying mechanism. Here, we reveal the perturbation of molecular order by methyl modification through molecular dynamics simulations, showing that methyl modification can increase membrane fluidity, explaining that this is a form of low-temperature acclimation. This hypothesis was also validated in environmental samples. This study reveals the role of methyl modifications in low-temperature adaptation in archaea, expanding that hydrophobic carbon chain methylation has unified physiological significance in three domain life. Our study highlights the role of molecular dynamics simulations in the development of lipid biomarkers, provides new insights into the mechanisms of temperature adaptation in microorganisms, and lays the groundwork for the development of new environmental proxies.