Complexity of the serpentinization lipidome

Abstract

Energy from serpentinization processes potentially fuelled the origin of life on Earth. Thus, if serpentinite-impacted sites facilitate microbial habitability, it is important to understand the source and retention of biological signatures in them. Investigating biological signatures in terrestrial serpentinite-impacted environments is also essential for interpreting molecular signature preservation on extraterrestrial bodies. To expand knowledge on the types of biological signatures derived from microorganisms in the serpentinization microbiome, mass spectrometry analysis was performed on Chimaera serpentinite rocks from Antalya Province, Turkey. The presence of diverse types of core and intact glycerol alkyl diether and tetraether lipids in all samples indicates that methanogenic archaea were present, but not in equal abundance in all rock types (carbonate or brucite) or locations (inside and outside the rock). Bacterial derived brGDGTs (branched glycerol dialkyl glycerol tetraethers) and phospholipid fatty acids were also identified in all samples. Comparing targeted lipid data from this study with other studies and locations reveals consistency across the serpentinization lipidome. Additionally, an untargeted lipidomics method was tested on the intact polar lipid (IPL) extracts, This resulted in detection of a wide range of intact lipids, many requiring further elucidation (e.g., diacyl glycerol IPLs, triacylglycerols, glycosphingolipids, sterol esters and cardiolipins), suggesting that there may be diverse bacterial, archaeal and fungal communities in the different rock samples, highlighting the additional complexity of the serpentinization lipidome dark matter.