title: Isolation of key methanogens for global methane emission from rice paddy fields: a novel isolate affiliated with the clone cluster rice cluster I.
abstract: Despite the fact that rice paddy fields (RPFs) are contributing 10 to 25% of global methane emissions, the organisms responsible for methane production in RPFs have remained uncultivated and thus uncharacterized. Here we report the isolation of a methanogen (strain SANAE) belonging to an abundant and ubiquitous group of methanogens called rice cluster I (RC-I) previously identified as an ecologically important microbial component via culture-independent analyses. To enrich the RC-I methanogens from rice paddy samples, we attempted to mimic the in situ conditions of RC-I on the basis of the idea that methanogens in such ecosystems should thrive by receiving low concentrations of substrate (H(2)) continuously provided by heterotrophic H(2)-producing bacteria. For this purpose, we developed a coculture method using an indirect substrate (propionate) in defined medium and a propionate-oxidizing, H(2)-producing syntroph, Syntrophobacter fumaroxidans, as the H(2) supplier. By doing so, we significantly enriched the RC-I methanogens and eventually obtained a methanogen within the RC-I group in pure culture. This is the first report on the isolation of a methanogen within RC-I.
authors.affiliation: Department of Environmental Systems Engineering, Nagaoka University of Technology, Nagaoka, Niigata, Japan.
authors.forename: Sanae
authors.initials: S
authors.lastname: Sakai
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Imachi
authors.forename: Yuji
authors.initials: Y
authors.lastname: Sekiguchi
authors.forename: Akiyoshi
authors.initials: A
authors.lastname: Ohashi
authors.forename: Hideki
authors.initials: H
authors.lastname: Harada
authors.forename: Yoichi
authors.initials: Y
authors.lastname: Kamagata
mesh_terms: D001105:Archaea / Q000145:classification / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism*; D001483:Base Sequence; D019641:DNA, Archaeal / Q000235:genetics; D017753:Ecosystem; D006859:Hydrogen / Q000378:metabolism; D008697:Methane / Q000378:metabolism*; D008969:Molecular Sequence Data; D012275:Oryza / Q000382:microbiology*; D010802:Phylogeny; D019642:RNA, Archaeal / Q000235:genetics; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D012988:Soil Microbiology
chemical_list: D019641:DNA, Archaeal; D019642:RNA, Archaeal; D012336:RNA, Ribosomal, 16S; D006859:Hydrogen; D008697:Methane