title: New insight into stratification of anaerobic methanotrophs in cold seep sediments.
abstract: Methane seepages typically harbor communities of anaerobic methane oxidizers (ANME); however, knowledge about fine-scale vertical variation of ANME in response to geochemical gradients is limited. We investigated microbial communities in sediments below a white microbial mat in the G11 pockmark at Nyegga by 16S rRNA gene tag pyrosequencing and real-time quantitative PCR. A vertical stratification of dominating ANME communities was observed at 4 cmbsf (cm below seafloor) and below in the following order: ANME-2a/b, ANME-1 and ANME-2c. The ANME-1 community was most numerous and comprised single or chains of cells with typical rectangular morphology, accounting up to 89.2% of the retrieved 16S rRNA gene sequences. Detection rates for sulfate-reducing Deltaproteobacteria possibly involved in anaerobic oxidation of methane were low throughout the core. However, a correlation in the abundance of Candidate division JS-1 with ANME-2 was observed, indicating involvement in metabolisms occurring in ANME-2-dominated horizons. The white microbial mat and shallow sediments were dominated by organisms affiliated with Sulfurovum (Epsilonproteobacteria) and Methylococcales (Gammaproteobacteria), suggesting that aerobic oxidation of sulfur and methane is taking place. In intermediate horizons, typical microbial groups associated with methane seeps were recovered. The data are discussed with respect to co-occurring microbial assemblages and interspecies interactions.
authors.affiliation: Department of Biology, Centre for Geobiology, University of Bergen, Norway.
authors.forename: Irene
authors.initials: I
authors.lastname: Roalkvam
authors.forename: Steffen Leth
authors.initials: SL
authors.lastname: Jørgensen
authors.forename: Yifeng
authors.initials: Y
authors.lastname: Chen
authors.forename: Runar
authors.initials: R
authors.lastname: Stokke
authors.forename: Håkon
authors.initials: H
authors.lastname: Dahle
authors.forename: William Peter
authors.initials: WP
authors.lastname: Hocking
authors.forename: Anders
authors.initials: A
authors.lastname: Lanzén
authors.forename: Haflidi
authors.initials: H
authors.lastname: Haflidason
authors.forename: Ida Helene
authors.initials: IH
authors.lastname: Steen
mesh_terms: D000693:Anaerobiosis; D001419:Bacteria / Q000145:classification / Q000235:genetics* / Q000378:metabolism; D018441:Biofilms / Q000254:growth & development; D020564:Deltaproteobacteria / Q000145:classification / Q000235:genetics / Q000378:metabolism; D019015:Geologic Sediments / Q000382:microbiology*; D008697:Methane / Q000378:metabolism*; D008969:Molecular Sequence Data; D012336:RNA, Ribosomal, 16S / Q000235:genetics / Q000378:metabolism; D060888:Real-Time Polymerase Chain Reaction; D012623:Seawater / Q000382:microbiology
chemical_list: D012336:RNA, Ribosomal, 16S; D008697:Methane