title: N2-dependent growth and nitrogenase activity in the metal-metabolizing bacteria, Geobacter and Magnetospirillum species.
abstract: Cells of Geobacter metallireducens, Magnetospirillum strain AMB-1, Magnetospirillum magnetotacticum and Magnetospirillum gryphiswaldense showed N2-dependent growth, the first anaerobically with Fe(III) as the electron acceptor, and the latter three species microaerobically in semi-solid oxygen gradient cultures. Cells of the Magnetospirillum species grown with N2 under microaerobic conditions were magnetotactic and therefore produced magnetosomes. Cells of Geobacter metallireducens reduced acetylene to ethylene (11.5+/-5.9 nmol C2H4 produced min(-1) mg(-1) cell protein) while growing with Fe(III) as the electron acceptor in anaerobic growth medium lacking a fixed nitrogen source. Cells of the Magnetospirillum species, grown in a semi-solid oxygen gradient medium, also reduced acetylene at comparable rates. Uncut chromosomal and fragments from endonuclease-digested chromosomal DNA from these species, as well as Geobacter sulphurreducens organisms, hybridized with a nifHDK probe from Rhodospirillum rubrum, indicating the presence of these nitrogenase structural genes in these organisms. The evidence presented here shows that members of the metal-metabolizing genera, Geobacter and Magnetospirillum, fix atmospheric dinitrogen.
authors.affiliation: Department of Microbiology, Iowa State University, Ames 50011, USA. dbazylin@iastate.edu
authors.forename: D A
authors.initials: DA
authors.lastname: Bazylinski
authors.forename: A J
authors.initials: AJ
authors.lastname: Dean
authors.forename: D
authors.initials: D
authors.lastname: Schüler
authors.forename: E J
authors.initials: EJ
authors.lastname: Phillips
authors.forename: D R
authors.initials: DR
authors.lastname: Lovley
mesh_terms: D000114:Acetylene / Q000378:metabolism; D004269:DNA, Bacterial / Q000032:analysis; D005030:Ethylenes / Q000096:biosynthesis; D005798:Genes, Bacterial; D007501:Iron / Q000378:metabolism*; D009586:Nitrogen Fixation / Q000235:genetics*; D009591:Nitrogenase / Q000378:metabolism*; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000378:metabolism; D020560:Proteobacteria / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D012244:Rhodospirillaceae / Q000235:genetics
chemical_list: D004269:DNA, Bacterial; D005030:Ethylenes; C036216:ethylene; D007501:Iron; D010088:Oxidoreductases; D009591:Nitrogenase; C029130:nitrogenase reductase; D000114:Acetylene