title: Evidence for syntrophic acetate oxidation coupled to hydrogenotrophic methanogenesis in the high-temperature petroleum reservoir of Yabase oil field (Japan).
abstract: The methanogenic communities and pathways in a high-temperature petroleum reservoir were investigated through incubations of the production water and crude oil, combined with radiotracer experiments and molecular biological analyses. The incubations were conducted without any substrate amendment and under high-temperature and pressurized conditions that mimicked the in situ environment (55°C, 5 MPa). Changes in methane and acetate concentrations during the incubations indicated stoichiometric production of methane from acetate. Rates of hydrogenotrophic methanogenesis measured using [(14)C]-bicarbonate were 42-68 times those of acetoclastic methanogenesis measured using [2-(14) C]-acetate, implying the dominance of methane production by syntrophic acetate oxidation coupled to hydrogenotrophic methanogenesis in the environment. 16S rRNA gene sequence analyses of the incubated production water showed bacterial communities dominated by the genus Thermacetogenium, known as a thermophilic syntrophic acetate-oxidizing bacterium, and archaeal communities dominated by thermophilic hydrogenotrophic methanogens belonging to the genus Methanothermobacter. Furthermore, group-specific real-time PCR assays revealed that 16S rRNA gene copy numbers of the hydrogenotrophic methanogens affiliated with the order Methanobacteriales were almost identical to those of archaeal 16S rRNA genes. This study demonstrates that syntrophic acetate oxidation is the main methanogenic pathway in a high-temperature petroleum reservoir.
authors.affiliation: Institute for Geo-Resources and Environment, National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Higashi, Tsukuba 305-8567, Japan.
authors.forename: Daisuke
authors.initials: D
authors.lastname: Mayumi
authors.forename: Hanako
authors.initials: H
authors.lastname: Mochimaru
authors.forename: Hideyoshi
authors.initials: H
authors.lastname: Yoshioka
authors.forename: Susumu
authors.initials: S
authors.lastname: Sakata
authors.forename: Haruo
authors.initials: H
authors.lastname: Maeda
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Miyagawa
authors.forename: Masayuki
authors.initials: M
authors.lastname: Ikarashi
authors.forename: Mio
authors.initials: M
authors.lastname: Takeuchi
authors.forename: Yoichi
authors.initials: Y
authors.lastname: Kamagata
mesh_terms: D000085:Acetates / Q000378:metabolism*; D001105:Archaea / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D001419:Bacteria / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D044822:Biodiversity; D004783:Environmental Microbiology; D006358:Hot Temperature; D007564:Japan; D008697:Methane / Q000096:biosynthesis*; D008969:Molecular Sequence Data; D061329:Oil and Gas Fields / Q000382:microbiology*; D010578:Petroleum / Q000378:metabolism; D010802:Phylogeny; D011312:Pressure; D012336:RNA, Ribosomal, 16S
chemical_list: D000085:Acetates; D010578:Petroleum; D012336:RNA, Ribosomal, 16S; D008697:Methane