title: Abundance, transcription levels and phylogeny of bacteria capable of nitrous oxide reduction in a municipal wastewater treatment plant.
abstract: Nitrous oxide (N2O) production and expression of genes capable of its reduction were investigated in two full-scale parallel plug-flow activated sludge systems. These two systems continuously received wastewater with the same constituents, but operated under distinct nitrification efficiencies due to mixed liquor suspended solid (MLSS) concentration and the different hydraulic retention times (HRTs). A shorter HRT in system 2 resulted in a lower nitrification efficiency (40-60%) in conjunction with a high N2O emission (50.6 mg-N/L/day), whereas there was a higher nitrification efficiency (>99%) in system 1 with low N2O emission (22.6 mg-N/L/day). The DNA abundance of functional genes responsible for nitrification and denitrification were comparable in both systems, but transcription of nosZ mRNA in the lower N2O emission system (system 1) was one order of magnitude higher than that in the higher N2O emission system (system 2). The diversity and evenness of the nosZ gene were nearly identical; however, the predominant N2O reducing bacteria were phylogenetically distinct. Phylogenetic analysis indicated that N2O-reducing strains only retrieved in system 1 were close to the genera Rhodobacter, Oligotropha and Shinella, whereas they were close to the genera Mesorhizobium only in system 2. The distinct predominant N2O reducers may directly or indirectly influence N2O emissions.
authors.affiliation: Department of Chemical Engineering, Tokyo University of Agriculture & Technology, Tokyo 184-8588, Japan.
authors.forename: Kang
authors.initials: K
authors.lastname: Song
authors.affiliation: Department of Chemical Engineering, Tokyo University of Agriculture & Technology, Tokyo 184-8588, Japan.
authors.forename: Toshikazu
authors.initials: T
authors.lastname: Suenaga
authors.affiliation: Tokyo Metropolitan Govt., Bur Sewerage, Tokyo 163-8001, Japan.
authors.forename: Aki
authors.initials: A
authors.lastname: Hamamoto
authors.affiliation: Tokyo Metropolitan Govt., Bur Sewerage, Tokyo 163-8001, Japan.
authors.forename: Kouichi
authors.initials: K
authors.lastname: Satou
authors.affiliation: Department of Chemical Engineering, Tokyo University of Agriculture & Technology, Tokyo 184-8588, Japan.
authors.forename: Shohei
authors.initials: S
authors.lastname: Riya
authors.affiliation: Department of Chemical Engineering, Tokyo University of Agriculture & Technology, Tokyo 184-8588, Japan.
authors.forename: Masaaki
authors.initials: M
authors.lastname: Hosomi
authors.affiliation: Department of Chemical Engineering, Tokyo University of Agriculture & Technology, Tokyo 184-8588, Japan. Electronic address: akte@cc.tuat.ac.jp.
authors.forename: Akihiko
authors.initials: A
authors.lastname: Terada
mesh_terms: D001419:Bacteria / Q000145:classification* / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D019149:Bioreactors; D058440:Denitrification; D058465:Nitrification; D009609:Nitrous Oxide / Q000378:metabolism*; D010084:Oxidation-Reduction; D010802:Phylogeny; D014158:Transcription, Genetic; D014865:Waste Disposal, Fluid; D062065:Wastewater / Q000382:microbiology*
chemical_list: D001426:Bacterial Proteins; D009609:Nitrous Oxide; D062065:Wastewater
keywords: Abundance of DNA and mRNA; Gene transcription; N(2)O reductase gene (nosZ); N(2)O reduction bacteria; Nitrous oxide reduction; Wastewater treatment plants