Fig 1.

Structures of diglycerol dialkyl tetraethers (GDGTs) core lipids synthesized by the studied soil thaumarchaeota. GDGT-0 to -4 are common archaeal GDGTs (15); crenarchaeol and its regioisomer were firstly identified in Cenarchaeum symbiosum (41). One example of a tentative structure of a hydroxylated GDGT is given (OH-GDGT-2). These types of GDGTs were recently identified by Liu et al. (20). At the right-hand side, general structures of IPLs detected in the studied soil thaumarchaeota are shown; polar head groups are shown in full structure: monohexose (MH), dihexose (DH), trihexose (TH), phosphohexose (PH), and hexose plus phosphohexose (HPH). It should be noted that the exact positions of the polar head groups are unknown.