Algal and archaeal polyisoprenoids in a recent marine sediment: Molecular isotopic evidence for anaerobic oxidation of methane

Abstract

Analyses of 13C contents of individual organic molecules in a marine sediment show that crocetane, 2,6,11,15‐tetramethylhexadecane, an isomer of phytane, is produced by microorganisms that use methane as their main source of carbon. The sediments lie at a water depth of 68 m in the Kattegat, the strait between Denmark and Sweden. Crocetane appears first 185 cm below the sediment‐water interface, in the zone marking the transition from sulfate reduction to methanogenesis. Its δ13C value is −90 ± 10‰ versus Vienna Pee Dee Belemnite (VPDB). Its structure, which includes four isoprene units arranged symmetrically around a tail‐to‐tail linkage, suggests that it is produced by a member of the archaea. Growing at the intersection of the diffusion gradients for sulfate and methane in sedimentary pore waters, the source organism apparently functions as a methane‐consuming member of the microbial consortium responsible for the anaerobic oxidation of methane [Hoehler et al., 1994], in which, as first demonstrated quantitatively in these sediments [Iversen and Jørgensen, 1985], electrons are transferred from methane to sulfate. The presence of archaeal biomass throughout the sediment section is indicated by significant concentrations of 2,6,10,15,19‐pentamethylicosane (PMI) and of ether‐bound phytane and biphytane. The PMI reaches a minimum δ value of −47‰ well below the transition zone. Its isotopic depletion could reflect either methanogenic or methanotrophic sources. The ether‐bound lipids are isotopically uniform throughout the section and are presumed to derive from archaea that utilize a carbon source unaffected by the oxidation of methane.

Growth and Methane Oxidation Rates of Anaerobic Methanotrophic Archaea in a Continuous-Flow Bioreactor

“…In total, the data presented here provides further support that MOA flourishing near one atmosphere may be adapted to maintain high methane oxidation rates per cell to attain the energy necessary for growth and reproduction. Empirical data of microbial populations and isotopic distributions, as well as theoretical models are also consistent with the growth of MOA near one atmosphere (1,7,31,35).…”

Methane emission and consumption at a North Sea gas seep (Tommeliten area)

“…Both ANME-1 and ANME-2 occur in consortia with relatives of a SRB cluster (Seep-SRB1) within the Desulfosarcina/Desulfococcus branch . Although the geology and biology of a variety of shallow water cold seeps have been well investigated, there is still very little known on the biogeochemistry and relevance of microbial methane consumption (Barry et al, 1996(Barry et al, , 1997Bian et al, 2001;Bussmann et al, 1999;Dando and Hovland, 1992;Garcia-Garcia et al, 2003;Thomsen et al, 2001). The aim of this investigation was to study microbial processes related to methane seepage in shelf sediments.…”

Impact of DOM composition on bacterial lipids and community structure in estuaries

“…Many members of the kingdom Archaea also have distinctive lipid signatures because of the unique sn-2, 3 rather than sn-1, 2 stereochemistry of the glycerol moiety and the presence of ether-bound membrane lipids with isoprenoidal carbon skeletons rather than ester-linked alkyl lipids (Koga et al 1998). The lipid signatures of Archaea have even been used to follow the distribution of groups which have not yet been successfully cultured (Bian et al 2001, Sturt et al 2004. Although it has long been suggested that bacterial community structure can be examined through fatty acid profiling (Guckert et al 1985), these acids vary greatly among culturable bacteria and others such as the branched acids do not appear to be universal (Kaneda 1991).…”