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N 2 ‐dependent growth and nitrogenase activity in the metal‐metabolizing bacteria, Geobacter and Magnetospirillum species
Author(s) -
Bazylinski Dennis A.,
Dean Annette J.,
Schüler Dirk,
Phillips Elizabeth J. P.,
Lovley Derek R.
Publication year - 2000
Publication title -
environmental microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.954
H-Index - 188
eISSN - 1462-2920
pISSN - 1462-2912
DOI - 10.1046/j.1462-2920.2000.00096.x
Subject(s) - nitrogenase , biology , electron acceptor , bacteria , microbiology and biotechnology , biochemistry , nitrogen fixation , genetics
Cells of Geobacter metallireducens , Magnetospirillum strain AMB‐1, Magnetospirillum magnetotacticum and Magnetospirillum gryphiswaldense showed N 2 ‐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 N 2 under microaerobic conditions were magnetotactic and therefore produced magnetosomes. Cells of Geobacter metallireducens reduced acetylene to ethylene (11.5 ± 5.9 nmol C 2 H 4 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.