title: Nitrogen fixation by the verrucomicrobial methanotroph 'Methylacidiphilum fumariolicum' SolV.
abstract: The ability to utilize atmospheric nitrogen (N(2)) as a sole nitrogen source is an important trait for prokaryotes. Knowledge of N(2) fixation by methanotrophs is needed to understand their role in nitrogen cycling in different environments. The verrucomicrobial methanotroph 'Methylacidiphilum fumariolicum' strain SolV was investigated for its ability to fix N(2). Physiological studies were combined with nitrogenase activity measurements and phylogenetic analysis of the nifDHK genes, encoding the subunits of the nitrogenase. 'M. fumariolicum' SolV was able to fix N(2) at low oxygen (O(2)) concentration (0.5 %, v/v) in chemostat cultures. This low oxygen concentration was also required for an optimal nitrogenase activity [47.4 nmol ethylene h(-1) (mg cell dry weight)(-1)]. Based on acetylene reduction assay and growth experiments, the nitrogenase of strain SolV seems to be extremely oxygen sensitive compared to most proteobacterial methanotrophs. The activity of the nitrogenase was not inhibited by ammonium concentrations up to 94 mM. This is believed to be the first report on the physiology of N(2) fixation within the phylum Verrucomicrobia.
authors.affiliation: Department of Microbiology, IWWR, Radboud University Nijmegen, Heyendaalseweg 135, NL-6525 AJ, Nijmegen, The Netherlands.
authors.forename: Ahmad F
authors.initials: AF
authors.lastname: Khadem
authors.affiliation: Department of Microbiology, IWWR, Radboud University Nijmegen, Heyendaalseweg 135, NL-6525 AJ, Nijmegen, The Netherlands.
authors.forename: Arjan
authors.initials: A
authors.lastname: Pol
authors.affiliation: Department of Microbiology, IWWR, Radboud University Nijmegen, Heyendaalseweg 135, NL-6525 AJ, Nijmegen, The Netherlands.
authors.forename: Mike S M
authors.initials: MSM
authors.lastname: Jetten
authors.affiliation: Department of Microbiology, IWWR, Radboud University Nijmegen, Heyendaalseweg 135, NL-6525 AJ, Nijmegen, The Netherlands.
authors.forename: Huub J M
authors.initials: HJM
authors.lastname: Op den Camp
mesh_terms: D001419:Bacteria / Q000145:classification / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D008697:Methane / Q000378:metabolism*; D008969:Molecular Sequence Data; D009584:Nitrogen / Q000378:metabolism; D009586:Nitrogen Fixation; D009591:Nitrogenase / Q000235:genetics / Q000378:metabolism; D010100:Oxygen / Q000378:metabolism; D010802:Phylogeny
chemical_list: D001426:Bacterial Proteins; D009591:Nitrogenase; D009584:Nitrogen; D008697:Methane; D010100:Oxygen