Intact membrane lipids of Candidatus "Nitrosopumilus maritimus", a cultivated representative of the cosmopolitan mesophilic Group I Crenarchaeota

Royal Netherlands Institute for Sea Research, Department of Marine Organic Biogeochemistry, PO Box 59, 1790 AB Den Burg, Texel, The Netherlands; Institute for Chemistry and Biology of the Marine Environment (ICBM), Carl von Ossietzky University of Oldenburg, PO Box 2503, 26111 Oldenburg, Germany; University of Washington, Civil and Environmental Engineering, 301 More Hall • Box 352700, Seattle, WA 98195-2700, USA

	Abstract

In this study we analysed the membrane lipid composition of Candidatus "Nitrosopumilus maritimus", the only cultivated representative of the cosmopolitan group I Crenarchaeota and the only mesophilic isolate of the phyla Crenarchaeota. The core lipids of N. maritimus consisted of glycerol dialkyl glycerol tetraethers (GDGTs) with 0-4 cyclopentyl moieties. Crenarchaeol, a unique GDGT containing a cyclohexyl moiety in addition to 4 cyclopentyl moieties, was the most abundant GDGT. This confirms unambiguously that crenarchaeol is synthesized by species belonging to the group I.1a Crenarchaeota. Intact polar lipid analysis revealed that the GDGTs have hexose, dihexose and/or phospho-hexose headgroups. Similar polar lipids were previous found in deeply buried sediments from the Peru margin, suggesting that they were in part synthesized by group I Crenarchaeota.