N2-dependent growth and nitrogenase activity in the metal-metabolizing bacteria, Geobacter and Magnetospirillum species

Environ Microbiol. 2000 Jun;2(3):266-73. doi: 10.1046/j.1462-2920.2000.00096.x.


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.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Acetylene / metabolism
  • DNA, Bacterial / analysis
  • Ethylenes / biosynthesis
  • Genes, Bacterial
  • Iron / metabolism*
  • Nitrogen Fixation / genetics*
  • Nitrogenase / metabolism*
  • Oxidation-Reduction
  • Oxidoreductases / metabolism
  • Proteobacteria / genetics
  • Proteobacteria / growth & development
  • Proteobacteria / metabolism*
  • Rhodospirillaceae / genetics


  • DNA, Bacterial
  • Ethylenes
  • ethylene
  • Iron
  • Oxidoreductases
  • Nitrogenase
  • nitrogenase reductase
  • Acetylene