title: Identification of the bacterial community involved in methane-dependent denitrification in activated sludge using DNA stable-isotope probing.
abstract: Methane is used as an alternative carbon source in the denitrification of wastewater lacking organic carbon sources because it is nontoxic and may be efficiently produced by anaerobic biological processes. Methane-dependent denitrification (MDD) in the presence of oxygen requires the co-occurrence of methanotrophy and denitrification. Activated sludge was incubated with 13C-labeled methane in either a nitrate-containing medium or a nitrate-free medium. Then, bacterial and methanotrophic populations were analyzed by cloning analysis and terminal restriction fragment length polymorphism analysis targeting 16S rRNA gene and cloning analysis targeting pmoA genes. DNA-based stable-isotope probing (DNA-SIP) analysis of the 16S rRNA gene revealed an association of the Methylococcaceae and the Hyphomicrobiaceae in a MDD ecosystem. Furthermore, supplementation of nitrate stimulated methane consumption and the activity of methanotrophic populations (i.e. the stimulation of uncultivated relatives of distinct groups of the Methylococcaceae). In particular, uncultured type-X methanotrophs of Gammaproteobacteria were dominant when nitrate was added, i.e. in the MDD incubations. On the other hand, most methanotrophs (types I, II, and X methanotrophs) were found to have been labeled with 13C under nitrate-free conditions. This DNA-SIP study identifies key bacterial populations involved in a MDD ecosystem.
authors.affiliation: Department of Chemical Engineering, Waseda University, Ohkubo, Shinjuku-ku, Tokyo, Japan.
authors.forename: Toshifumi
authors.initials: T
authors.lastname: Osaka
authors.forename: Yoshitaka
authors.initials: Y
authors.lastname: Ebie
authors.forename: Satoshi
authors.initials: S
authors.lastname: Tsuneda
authors.forename: Yuhei
authors.initials: Y
authors.lastname: Inamori
mesh_terms: D001419:Bacteria / Q000145:classification* / Q000235:genetics / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics; D044822:Biodiversity; D016172:DNA Fingerprinting; D015342:DNA Probes; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D004275:DNA, Ribosomal / Q000737:chemistry / Q000235:genetics; D017753:Ecosystem; D007553:Isotope Labeling; D008697:Methane / Q000378:metabolism*; D008969:Molecular Sequence Data; D009584:Nitrogen / Q000378:metabolism*; D012150:Polymorphism, Restriction Fragment Length; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D017422:Sequence Analysis, DNA; D012722:Sewage / Q000382:microbiology*
chemical_list: D001426:Bacterial Proteins; D015342:DNA Probes; D004269:DNA, Bacterial; D004275:DNA, Ribosomal; D012336:RNA, Ribosomal, 16S; D012722:Sewage; D009584:Nitrogen; D008697:Methane