title: Ammonium conversion and its feedback effect on methane oxidation of Methylosinus sporium.
abstract: Ammonium (NH4+) is not only nitrogen source that can support methanotrophic growth, but also it can inhibit methane (CH4) oxidation by competing with CH4for the active site of methane monooxygenase. NH4+conversion and its feedback effect on the growth and activity of methanotrophs were evaluated with Methylosinus sporium used as a model methanotroph. Nitrogen sources could affect the CH4-derived carbon distribution, which varied with incubation time and nitrogen concentrations. More CH4-derived carbon was incorporated into biomass in the media with NH4+-N, compared to nitrate-nitrogen (NO3--N), as sole nitrogen source at the nitrogen concentrations of 10-18 mmol L-1. Although ammonia (NH3) oxidation activity of methanotrophs was considerably lower, only accounting for 0.01-0.06% of CH4oxidation activity in the experimental cultures, NH4+conversion could lead to the pH decrease and toxic intermediates accumulation in the their habits. Compared with NH4+, nitrite (NO2-) accumulation in the NH4+conversion of methanotroph had stronger inhibition on its activity, especially the joint inhibition of NO2-accumulation and the pH decrease during the NH4+-N conversion. These results suggested that more attention should be paid to the feedback effects of NH4+conversion by methanotrophs to understand effects of NH4+on CH4oxidation in the environments.
authors.affiliation: Department of Environmental Engineering, Zhejiang University, Hangzhou 310058, China. Electronic address: heruo@zju.edu.cn.
authors.forename: Ruo
authors.initials: R
authors.lastname: He
authors.affiliation: Department of Environmental Engineering, Zhejiang University, Hangzhou 310058, China.
authors.forename: Min
authors.initials: M
authors.lastname: Chen
authors.affiliation: Department of Environmental Engineering, Zhejiang University, Hangzhou 310058, China.
authors.forename: Ruo-Chan
authors.initials: RC
authors.lastname: Ma
authors.affiliation: Department of Environmental Engineering, Zhejiang University, Hangzhou 310058, China.
authors.forename: Yao
authors.initials: Y
authors.lastname: Su
authors.affiliation: Department of Environmental Engineering, Zhejiang University, Hangzhou 310058, China.
authors.forename: Xuan
authors.initials: X
authors.lastname: Zhang
mesh_terms: D000641:Ammonia / Q000378:metabolism; D064751:Ammonium Compounds / Q000378:metabolism*; D001667:Binding, Competitive; D018533:Biomass; D020134:Catalytic Domain; D025461:Feedback, Physiological; D006863:Hydrogen-Ion Concentration; D008697:Methane / Q000378:metabolism*; D020581:Methylosinus / Q000201:enzymology / Q000254:growth & development / Q000378:metabolism*; D009566:Nitrates / Q000378:metabolism; D009573:Nitrites / Q000378:metabolism; D009584:Nitrogen / Q000378:metabolism; D010084:Oxidation-Reduction; D010105:Oxygenases / Q000737:chemistry / Q000378:metabolism
chemical_list: D064751:Ammonium Compounds; D009566:Nitrates; D009573:Nitrites; D000641:Ammonia; D010105:Oxygenases; C021555:methane monooxygenase; D009584:Nitrogen; D008697:Methane
keywords: Ammonium conversion; Methane oxidation; Methane-derived carbon; Methanotroph; Nitrification