title: Crenarchaeol dominates the membrane lipids of Candidatus Nitrososphaera gargensis, a thermophilic group I.1b Archaeon.
abstract: Analyses of archaeal membrane lipids are increasingly being included in ecological studies as a comparatively unbiased complement to gene-based microbiological approaches. For example, crenarchaeol, a glycerol dialkyl glycerol tetraether (GDGT) with a unique cyclohexane moiety, has been postulated as biomarker for ammonia-oxidizing Archaea (AOA). Crenarchaeol has been detected in Nitrosopumilus maritimus and 'Candidatus Nitrosocaldus yellowstonii' representing two of the three lineages within the Crenarchaeota containing described AOA. In this paper we present the membrane GDGT composition of 'Candidatus Nitrososphaera gargensis', a moderately thermophilic AOA, and the only cultivated Group I.1b Crenarchaeon. At a cultivation temperature of 46 degrees C, GDGTs of this organism consisted primarily of crenarchaeol, its regioisomer, and a novel GDGT. Intriguingly, 'Ca. N. gargensis' is the first cultivated archaeon to synthesize substantial amounts of the crenarchaeol regioisomer, a compound found in large relative abundances in tropical ocean water and some soils, and an important component of the TEX(86) paleothermometer. Intact polar lipid (IPL) analysis revealed that 'Ca. N. gargensis' synthesizes IPLs similar to those reported for the Goup I.1a AOA, Nitrosopumilus maritimus SCMI, in addition to IPLs containing uncharacterized headgroups. Overall, the unique GDGT composition of 'Ca. N. gargensis' extends the known taxonomic distribution of crenarchaeol synthesis to the Group I.1b Crenarchaeota, implicating this clade as a potentially important source of crenarchaeol in soils and moderately high temperature environments. Moreover, this work supports the hypothesis that crenarchaeol is specific to all AOA and highlights specific lipids, which may prove useful as biomarkers for 'Ca. N. gargensis'-like AOA.
authors.affiliation: Department of Marine Organic Biogeochemistry, NIOZ Royal Netherlands Institute for Sea Research, Den Burg, The Netherlands. apitcher@nioz.nl
authors.forename: Angela
authors.initials: A
authors.lastname: Pitcher
authors.forename: Nicolas
authors.initials: N
authors.lastname: Rychlik
authors.forename: Ellen C
authors.initials: EC
authors.lastname: Hopmans
authors.forename: Eva
authors.initials: E
authors.lastname: Spieck
authors.forename: W Irene C
authors.initials: WI
authors.lastname: Rijpstra
authors.forename: Jort
authors.initials: J
authors.lastname: Ossebaar
authors.forename: Stefan
authors.initials: S
authors.lastname: Schouten
authors.forename: Michael
authors.initials: M
authors.lastname: Wagner
authors.forename: Jaap S Sinninghe
authors.initials: JS
authors.lastname: Damsté
mesh_terms: D019615:Crenarchaeota / Q000737:chemistry* / Q000145:classification / Q000254:growth & development / Q000302:isolation & purification; D005995:Glyceryl Ethers / Q000032:analysis*; D006358:Hot Temperature; D008563:Membrane Lipids / Q000032:analysis*; D012988:Soil Microbiology; D013237:Stereoisomerism
chemical_list: D005995:Glyceryl Ethers; D008563:Membrane Lipids; C493345:crenarchaeol