title: A distinct freshwater-adapted subgroup of ANME-1 dominates active archaeal communities in terrestrial subsurfaces in Japan.
abstract: Anaerobic methane-oxidizing archaea (ANME) are known to play an important role in methane flux, especially in marine sediments. The 16S rRNA genes of ANME have been detected in terrestrial freshwater subsurfaces. However, it is unclear whether ANME are actively involved in methane oxidation in these environments. To address this issue, Holocene sediments in the subsurface of the Kanto Plain in Japan were collected for biogeochemical and molecular analysis. The potential activity of the anaerobic oxidation of methane (AOM) (0.38-3.54 nmol cm⁻³ day⁻¹) was detected in sediment slurry incubation experiments with a (13) CH(4) tracer. Higher AOM activity was observed in low-salinity treatment compared with high-salinity condition (20‰), which supports the adaptation of ANME in freshwater habitats. The 16S rRNA sequence analysis clearly revealed the presence of a distinct subgroup of ANME-1, designated ANME-1a-FW. Phylogenetic analysis of the mcrA genes also implied the presence of the distinct subgroup in ANME-1. ANME-1a-FW was found to be the most dominant active group in the archaeal communities on the basis of 16S rRNA analysis (75.0-93.8% of total archaeal 16S rRNA clones). Sulfate-reducing bacteria previously known as the syntrophic bacterial partners of ANME-1 was not detected. Our results showed that ANME-1a-FW is adapted to freshwater habitats and is responsible for AOM in terrestrial freshwater subsurface environments.
authors.affiliation: Institute for Geo-resources and Environments, National Institute of Advanced Industrial Science and Technology (AIST), 16-1 Onogawa, Tsukuba, Ibaraki 305-8569, Japan. takeuchi-mio@aist.go.jp
authors.forename: Mio
authors.initials: M
authors.lastname: Takeuchi
authors.forename: Hideyoshi
authors.initials: H
authors.lastname: Yoshioka
authors.forename: Yuna
authors.initials: Y
authors.lastname: Seo
authors.forename: Susumu
authors.initials: S
authors.lastname: Tanabe
authors.forename: Hideyuki
authors.initials: H
authors.lastname: Tamaki
authors.forename: Yoichi
authors.initials: Y
authors.lastname: Kamagata
authors.forename: Hiroshi A
authors.initials: HA
authors.lastname: Takahashi
authors.forename: Shunichiro
authors.initials: S
authors.lastname: Igari
authors.forename: Daisuke
authors.initials: D
authors.lastname: Mayumi
authors.forename: Susumu
authors.initials: S
authors.lastname: Sakata
mesh_terms: D000220:Adaptation, Biological; D000693:Anaerobiosis; D001105:Archaea / Q000145:classification* / Q000235:genetics / Q000378:metabolism; D001419:Bacteria / Q000145:classification / Q000235:genetics; D019641:DNA, Archaeal / Q000235:genetics; D017753:Ecosystem; D005618:Fresh Water / Q000737:chemistry / Q000382:microbiology*; D015723:Gene Library; D019015:Geologic Sediments / Q000737:chemistry / Q000382:microbiology*; D007564:Japan; D008697:Methane / Q000378:metabolism*; D008969:Molecular Sequence Data; D010084:Oxidation-Reduction; D010802:Phylogeny; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D054712:Salinity; D014871:Water Microbiology
chemical_list: D019641:DNA, Archaeal; D012336:RNA, Ribosomal, 16S; D008697:Methane