title: N2O and N2 production during heterotrophic nitrification by Alcaligenes faecalis strain NR.
abstract: A heterotrophic nitrifier, strain NR, was isolated from a membrane bioreactor. Strain NR was identified as Alcaligenes faecalis by Auto-Microbic system and 16S rRNA gene sequence analysis. A. faecalis strain NR shows a capability of heterotrophic nitrification and N(2)O and N(2) production as well under the aerobic condition. Further tests demonstrated that neither nitrite nor nitrate could be denitrified aerobically by strain NR. However, when hydroxylamine was used as the sole nitrogen source, nitrogenous gases were detected. With an enzyme assay, a 0.063 U activity of hydroxylamine oxidase was observed, while nitrate reductase and nitrite reductase were undetectable. Thus, nitrogenous gas was speculated to be produced via hydroxylamine. Therefore, two different metabolic pathways might exist in A. faecalis NR. One is heterotrophic nitrification by oxidizing ammonium to nitrite and nitrate. The other is oxidizing ammonium to nitrogenous gas directly via hydroxylamine.
authors.affiliation: The Key Laboratory of Eco-environments in Three Gorges Reservoir Region, Chongqing University, Chongqing 400045, PR China. binzhao11@cqu.edu.cn
authors.forename: Bin
authors.initials: B
authors.lastname: Zhao
authors.forename: Qiang
authors.initials: Q
authors.lastname: An
authors.forename: Yi Liang
authors.initials: YL
authors.lastname: He
authors.forename: Jin Song
authors.initials: JS
authors.lastname: Guo
mesh_terms: D000332:Aerobiosis / Q000187:drug effects; D042481:Alcaligenes faecalis / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D001483:Base Sequence; D002244:Carbon / Q000494:pharmacology; D003470:Culture Media / Q000494:pharmacology; D057075:Enzyme Assays; D052836:Heterotrophic Processes / Q000187:drug effects / Q000502:physiology*; D019811:Hydroxylamine / Q000378:metabolism; D053858:Metabolic Networks and Pathways / Q000187:drug effects; D008969:Molecular Sequence Data; D009566:Nitrates / Q000378:metabolism; D058465:Nitrification / Q000502:physiology*; D009572:Nitrite Reductases / Q000378:metabolism; D009573:Nitrites / Q000378:metabolism; D009584:Nitrogen / Q000378:metabolism* / Q000494:pharmacology; D009609:Nitrous Oxide / Q000378:metabolism*; D010802:Phylogeny; D000644:Quaternary Ammonium Compounds / Q000302:isolation & purification; D012336:RNA, Ribosomal, 16S / Q000235:genetics
chemical_list: D003470:Culture Media; D009566:Nitrates; D009573:Nitrites; D000644:Quaternary Ammonium Compounds; D012336:RNA, Ribosomal, 16S; D019811:Hydroxylamine; D002244:Carbon; D009572:Nitrite Reductases; D009609:Nitrous Oxide; D009584:Nitrogen