An unusual isoprenoid tetraether lipid in marine and lacustrine sediments

Recent studies have shown that glycerol dialkyl glycerol tetraether (GDGT) lipids, thought be unique for (hyper)thermophilic archaea, are also present in non-thermophilic archaea and environments. In this study, an unusual H-shaped isoprenoid GDGT, in which the two biphytanyl carbon skeletons are covalently bound by a carbon–carbon bond, was unambiguously identified in a number of sediments from marine and lacustrine environments. Its abundance varies from 0.2% to 6% of isoprenoid GDGTs. The H-shaped isoprenoid GDGT was originally identified in hyperthermophilic archaea and its presence in marine and lacustrine sediments suggests it is also synthesized by certain non-thermophilic relatives, possibly Euryarchaeota.