Membrane lipids of mesophilic anaerobic bacteria thriving in peats have typical archaeal traits.

The 16S ribosomal DNA based distinction between the bacterial and archaeal domains of life is strongly supported by the membrane lipid composition of the two domains; Bacteria generally contain dialkyl glycerol diester lipids, whereas Archaea produce isoprenoid dialkyl glycerol diether and membrane-spanning glycerol dialkyl glycerol tetraether (GDGT) lipids. Here we show that a new group of ecologically abundant membrane-spanning GDGT lipids, containing branched instead of isoprenoid carbon skeletons, are of a bacterial origin. This was revealed by examining the stereochemistry of the glycerol moieties of those branched tetraether membrane lipids, which was found to be the bacterial 1,2-di-O-alkyl-sn-glycerol stereoconfiguration and not the 2,3-di-O-alkyl-sn-glycerol stereoconfiguration as in archaeal membrane lipids.

Lipid biomolecules in silica sinters: indicators of microbial biodiversity.

To explore further the diversity of the microorganisms and their relationship with geothermal sinters, we examined the lipids preserved in six sinters associated with four different hot spring (58-82 degrees C) areas of the Taupo Volcanic Zone (TVZ), New Zealand. These sinters contain microbial remains, but the process of mineralization has rendered them largely unidentifiable. Dominant lipids include free fatty acids, 1,2-diacylglycerophospholipids, 1,2-di-O-alkylglycerols, glycerol dialkylglycerol tetraethers and 1-O-alkylglycerols.