Identification of isoprenoid glycosidic glycerol dibiphytanol diethers and indications for their biosynthetic origin

A series of archaeal lipid biomarkers, the isoprenoid glycerol dibiphytanol diethers (GDDs), was recently described and proposed to represent either biosynthetic intermediates or diagenetic products of the relatively more abundant glycerol dibiphytanyl glycerol tetraether (GDGT) lipids (Liu, X.-L., Lipp, J.S., Schröder, J.M., Summons, R.E., Hinrichs, K.-U., 2012. Isoprenoid glycerol dialkanol diethers: a series of novel lipids in marine sediments. Organic Geochemistry 43, 50-55). Here we report a novel series of polar lipids comprising a glycosidic head group and GDD core lipids with varying cycloalkyl distributions (1G-GDDs), which were found in estuarine and hot spring sediments, as well as in a pure culture of the mesophilic thaumarchaeon Nitrosopumilus maritimus. 1G-GDDs represented up to 4% of the corresponding monoglycosidic GDGTs (1G-GDGTs). The distinct cycloalkyl distribution patterns of these intact polar lipids (IPLs) and detection of 1G-GDDs in an archaeal culture suggest a biosynthetic source of 1G-GDDs rather than formation exclusively via diagenetic removal of a glycerol moiety from 1G-GDGTs.