title: Characterization of a spontaneous mutant of Azotobacter vinelandii in which vanadium-dependent nitrogen fixation is not inhibited by molybdenum.
abstract: A spontaneous mutant derivative of Azotobacter vinelandii CA12 (delta nif HDK), which vanadium-dependent nitrogen fixation is not inhibited by molybdenum (A. vinelandii CARR), grows profusely on BNF-agar containing 1 microM Na2MoO4, alone or supplemented with 1 microM V2O5. The expression of A. vinelandii vnfH::lacZ and vnfA::lacZ fusions in A. vinelandii CARR was not inhibited by 1 mM Na2MoO4, whereas molybdenum at much lower concentration inhibited the expression of vnfH::lacZ and vnfA::lacZ fusions in A. vinlandii CA12. The mutant also exhibited normal acetylene reduction activity in the presence of 1 microM Na2MoO4. The expression of A. vinelandii nifH::lacZ fusion in A. vinelandii CARR was low even though the cells were cultured under non-repressing conditions with urea as nitrogen source in the presence of Na2MoO4. The molybdenum content of A. vinelandii CARR cells was found to be about one-fourth that of A. vinelandii CA12. No nitrate reductase activity could be detected in A. vinelandii CARR when the cells were cultured in the presence of 10 microM Na2MoO4, whereas A. vinelandii CA12 exhibited some activity even with 100 pM Na2MoO4.
authors.affiliation: Genetic Engineering Unit, Jawaharlal Nehru University, New Delhi, India.
authors.forename: U K
authors.initials: UK
authors.lastname: Bageshwar
authors.forename: R
authors.initials: R
authors.lastname: Raina
authors.forename: H K
authors.initials: HK
authors.lastname: Das
mesh_terms: D000114:Acetylene / Q000378:metabolism; D016948:Azotobacter vinelandii / Q000737:chemistry / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D015870:Gene Expression; D008982:Molybdenum / Q000032:analysis / Q000494:pharmacology*; D009154:Mutation / Q000502:physiology*; D050901:Nitrate Reductase; D009565:Nitrate Reductases / Q000378:metabolism; D009586:Nitrogen Fixation / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D009591:Nitrogenase / Q000235:genetics; D010084:Oxidation-Reduction; D010088:Oxidoreductases; D011993:Recombinant Fusion Proteins; D017973:Tungsten Compounds / Q000494:pharmacology; D014639:Vanadium / Q000502:physiology*; D017968:Vanadium Compounds / Q000494:pharmacology
chemical_list: D011993:Recombinant Fusion Proteins; D017973:Tungsten Compounds; D017968:Vanadium Compounds; D014639:Vanadium; C025399:sodium tungstate(VI); D008982:Molybdenum; C024687:sodium molybdate(VI); C066075:vanadium pentoxide; D010088:Oxidoreductases; D009591:Nitrogenase; C029130:nitrogenase reductase; D009565:Nitrate Reductases; D050901:Nitrate Reductase; D000114:Acetylene