title: Mono-, di- and trimethylated homologues of isoprenoid tetraether lipid cores in archaea and environmental samples: mass spectrometric identification and significance.
abstract: Higher homologues of widely reported C(86) isoprenoid diglycerol tetraether lipid cores, containing 0-6 cyclopentyl rings, have been identified in (hyper)thermophilic archaea, representing up to 21% of total tetraether lipids in the cells. Liquid chromatography-tandem mass spectrometry confirms that the additional carbon atoms in the C(87-88) homologues are located in the etherified chains. Structures identified include dialkyl and monoalkyl ('H-shaped') tetraethers containing C(40-42) or C(81-82) hydrocarbons, respectively, many representing novel compounds. Gas chromatography-mass spectrometric analysis of hydrocarbons released from the lipid cores by ether cleavage suggests that the C(40) chains are biphytanes and the C(41) chains 13-methylbiphytanes. Multiple isomers, having different chain combinations, were recognised among the dialkyl lipids. Methylated tetraethers are produced by Methanothermobacter thermautotrophicus in varying proportions depending on growth conditions, suggesting that methylation may be an adaptive mechanism to regulate cellular function. The detection of methylated lipids in Pyrobaculum sp. AQ1.S2 and Sulfolobus acidocaldarius represents the first reported occurrences in Crenarchaeota. Soils and aquatic sediments from geographically distinct mesotemperate environments that were screened for homologues contained monomethylated tetraethers, with di- and trimethylated structures being detected occasionally. The structural diversity and range of occurrences of the C(87-89) tetraethers highlight their potential as complementary biomarkers for archaea in natural environments.
authors.affiliation: Department of Chemistry, University of York, York, YO10 5DD, UK.
authors.forename: Chris
authors.initials: C
authors.lastname: Knappy
authors.affiliation: Department of Biology, University of York, York, YO10 5DD, UK.
authors.forename: Daniela
authors.initials: D
authors.lastname: Barillà
authors.affiliation: Department of Biology, University of York, York, YO10 5DD, UK.
authors.forename: James
authors.initials: J
authors.lastname: Chong
authors.affiliation: British Antarctic Survey, Madingley Road, Cambridge, CB3 0ET, UK.
authors.forename: Dominic
authors.initials: D
authors.lastname: Hodgson
authors.affiliation: Thermophile Research Unit, University of Waikato, Hamilton, New Zealand.
authors.forename: Hugh
authors.initials: H
authors.lastname: Morgan
authors.affiliation: Department of Chemistry, University of York, York, YO10 5DD, UK.|Department of Agricultural Chemistry, Agricultural University, Peshawar, 25130, Khyber Pakhtunkhwa, Pakistan.
authors.forename: Muhammad
authors.initials: M
authors.lastname: Suleman
authors.affiliation: Thermophile Research Unit, University of Waikato, Hamilton, New Zealand.
authors.forename: Christine
authors.initials: C
authors.lastname: Tan
authors.affiliation: Department of Chemistry, University of York, York, YO10 5DD, UK.|Key Laboratory of Marine Chemistry Theory and Technology, Ministry of Education, Ocean University of China, Qingdao, 266100, China.
authors.forename: Peng
authors.initials: P
authors.lastname: Yao
authors.affiliation: Department of Chemistry, University of York, York, YO10 5DD, UK.
authors.forename: Brendan
authors.initials: B
authors.lastname: Keely
mesh_terms: D001105:Archaea / Q000737:chemistry*; D002853:Chromatography, Liquid; D004075:Diglycerides / Q000737:chemistry*; D008745:Methylation; D053719:Tandem Mass Spectrometry; D013729:Terpenes / Q000737:chemistry*
chemical_list: D004075:Diglycerides; D013729:Terpenes; C567981:diglyceryl-tetraether
keywords: GDGT; LC-MS/MS; archaea; isoprenoid; methylated tetraether lipid homologue