Reappraisal of archaeal C20-C25 diether lipid (extended archaeol) origin and use as a biomarker of hypersalinity

The diether core membrane lipid sesterterpanyl-phytanyl-glycerol (so-called extended archaeol and often abbreviated C20-C25) is considered as a hallmark of Haloarchaea, clade archaea thriving under extreme high salinities. We here report about occurrence in different saline aquatic settings with salinity ranging from ca. 50 psu (5 % NaCl w/v) to saturation (ca. 350 psu). This demonstrates that this not restricted environments but suggests minimum threshold above which C20-C25 most commonly produced. proportion relative (C20-C20) did appear linearly dependent on the site was potentially also influenced by pH temperature, preventing its direct use quantitative proxy based present data set. An extensive literature review archaeal compositions further highlighted taxonomy contributes distribution environment identifies Natrialbales (one three orders Haloarchaea) main source. Statistical analysis showed that, among producers display growth optima slightly higher than non-producers are distributed within two distinct groups, one composed mostly neutrophiles alkaliphiles. In contrast, presence correlated optimal temperature strains. confounding parameters, i.e., adaptation changes and/or pH, contribute Haloarchaea.