title: Ammonium and hydroxylamine uptake and accumulation in Nitrosomonas.
abstract: Starved cells of Nitrosomonas europaea and further ammonia oxidizers were able to rapidly accumulate ammonium and hydroxylamine to an internal concentration of about 1 and 0.8 M, respectively. In kinetic studies, the uptake/accumulation rates for ammonium [3.1 mmol (g protein)(-1) min(-1)] and hydroxylamine [4.39 mmol (g protein)(-1) min(-1)] were determined. The uptake and accumulation process of ammonium and hydroxylamine was not coupled to ammonia or hydroxylamine oxidation and nitrite was not produced. In the presence of uncouplers the ammonium accumulation was completely inhibited, indicating an active, membrane-potential-driven transport mechanism. When the external ammonium or hydroxylamine pool was depleted, the internal ammonium and hydroxylamine was consumed within 12 h or 20 min, respectively. The binding of ammonium/ammonia was correlated with an energized membrane system, and hydroxylamine may bind to the hydroxylamine oxidoredutase.
authors.affiliation: Department of Microbiology, University of Bayreuth, Universitaetsstrasse 30, 95447 Bayreuth, Germany.
authors.forename: Ingo
authors.initials: I
authors.lastname: Schmidt
authors.affiliation: Department of Microbiology, University of Hamburg, Ohnhorststrasse 18, 22609 Hamburg, Germany.
authors.forename: Christiane
authors.initials: C
authors.lastname: Look
authors.affiliation: Department of Microbiology, University of Hamburg, Ohnhorststrasse 18, 22609 Hamburg, Germany.
authors.forename: Eberhard
authors.initials: E
authors.lastname: Bock
authors.affiliation: Department of Microbiology, University of Nijmegen, Toernooiveld 1, 6525 ED Nijmegen, The Netherlands.
authors.forename: Mike S M
authors.initials: MSM
authors.lastname: Jetten
mesh_terms: D003470:Culture Media; D015964:Gene Expression Regulation, Bacterial; D019811:Hydroxylamine / Q000378:metabolism*; D009573:Nitrites / Q000378:metabolism; D009587:Nitrogen Isotopes / Q000378:metabolism; D009606:Nitrosomonas / Q000378:metabolism* / Q000502:physiology; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000378:metabolism; D000644:Quaternary Ammonium Compounds / Q000378:metabolism*
chemical_list: D003470:Culture Media; D009573:Nitrites; D009587:Nitrogen Isotopes; D000644:Quaternary Ammonium Compounds; D019811:Hydroxylamine; D010088:Oxidoreductases