title: Microbial diversity and methanogenic potential in a high temperature natural gas field in Japan.
abstract: Microbial diversity and methanogenic potential in formation water samples from a dissolved-in-water type gas field were investigated by using 16S rRNA gene libraries and culture-based methods. Two formation water samples (of 46 and 53 degrees C in temperature) were obtained from a depth of 700 to 800 m. Coenzyme F(420)-autofluorescence indicated that 10(3)-10(4) cells per ml of active methanogens were present, accounting for at least 10% of the total cell count. The 16S rRNA gene sequence analysis indicated that the diversity of Archaea and Bacteria of the two samples was quite limited; i.e., the archaeal libraries were dominated by the sequences related to Methanobacterium formicicum and Methanothermobacter thermautotrophicus, and the bacterial libraries were dominated by the sequences related to Hydrogenophilus and Deferribacter. Of the methanogenic substrates tested using the formation water-based medium, only H(2)-CO(2) gave rise to methane formation. Those dominant archaeal and bacterial genera have the potential to use hydrogen for growth at the in situ temperatures, suggesting that the formation water of the Pliocene strata in the gas field has been provided with hydrogen, probably from underneath the strata, and thus on-going active methanogenesis has been occurring to date.
authors.affiliation: Graduate School of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Ibaraki, 305-8572, Japan.
authors.forename: Hanako
authors.initials: H
authors.lastname: Mochimaru
authors.forename: Hideyoshi
authors.initials: H
authors.lastname: Yoshioka
authors.forename: Hideyuki
authors.initials: H
authors.lastname: Tamaki
authors.forename: Kohei
authors.initials: K
authors.lastname: Nakamura
authors.forename: Nobuyuki
authors.initials: N
authors.lastname: Kaneko
authors.forename: Susumu
authors.initials: S
authors.lastname: Sakata
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Imachi
authors.forename: Yuji
authors.initials: Y
authors.lastname: Sekiguchi
authors.forename: Hiroo
authors.initials: H
authors.lastname: Uchiyama
authors.forename: Yoichi
authors.initials: Y
authors.lastname: Kamagata
mesh_terms: D001105:Archaea / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D017931:DNA Primers; D006358:Hot Temperature; D007564:Japan; D008697:Methane / Q000378:metabolism*; D010802:Phylogeny; D012336:RNA, Ribosomal, 16S / Q000235:genetics
chemical_list: D017931:DNA Primers; D012336:RNA, Ribosomal, 16S; D008697:Methane