title: Nitrogen fixation system of tungsten-resistant mutants of Azotobacter vinelandii.
abstract: Mutants of Azotobacter vinelandii ATCC 12837 were isolated which could fix N2 in the presence of high tungsten concentrations. The most studied of these mutants (WD2) grew well in N-free modified Burk broth containing 10 mM W, whereas the wild type would not grow in this medium. WD2 would also grow in Burk N-free broth at about the same rate as the wild type. WD2 in broth containing W exhibited 22% of the whole cell acetylene reduction activity of the wild type in broth containing Mo and showed a lowered affinity for acetylene. Two-dimensional gel electrophoresis experiments showed that N2-fixing cells of WD2 from broth containing W or Mo did not produce significant amounts of component I of native nitrogenase protein. Electron spin resonance spectra of whole cells and cell-free extracts of WD2 from broth containing W lacked any trace of the g = 3.6 resonance associated with FeMoCo.
mesh_terms: D000114:Acetylene / Q000378:metabolism; D001395:Azotobacter / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D004352:Drug Resistance, Microbial; D008982:Molybdenum / Q000494:pharmacology; D009154:Mutation; D009586:Nitrogen Fixation; D009591:Nitrogenase / Q000032:analysis; D010084:Oxidation-Reduction; D014414:Tungsten / Q000494:pharmacology*
chemical_list: D008982:Molybdenum; D009591:Nitrogenase; D000114:Acetylene; D014414:Tungsten