Intact polar lipid and core lipid inventory of the hydrothermal vent methanogens Methanocaldococcus villosus and Methanothermococcus okinawensis

•Occurrence of a second GMGT-0 isomer in M. villosus and M. okinawensis.•GTGT-0 and GMGT-0 reported for the first time in the order Methanococcales.•First detection of macrocyclic archaeol in the genus Methanothermococcus.•Identical core lipid inventory in both strains, but different polar head groups.