Open AccessCharacterization of a spontaneous mutant of Azotobacter vinelandii in which vanadium‐dependent nitrogen fixation is not inhibited by molybdenum
Author(s) -
Bageshwar Umesh K,
Raina Ramesh,
Das H.K
Publication year - 1998
Publication title -
fems microbiology letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.899
H-Index - 151
eISSN - 1574-6968
pISSN - 0378-1097
DOI - 10.1111/j.1574-6968.1998.tb12994.x
Subject(s) - azotobacter vinelandii , nitrate reductase , nitrogenase , mutant , chemistry , nitrogen fixation , biochemistry , microbiology and biotechnology , biology , nitrogen , enzyme , gene , organic chemistry
A spontaneous mutant derivative of Azotobacter vinelandii CA12 (Δ nifHDK ), in which vanadium‐dependent nitrogen fixation is not inhibited by molybdenum ( A. vinelandii CARR), grows profusely on BNF‐agar containing 1 μM Na 2 MoO 4 , alone or supplemented with 1 μM V 2 O 5 . The expression of A. vinelandii vnfH::lacZ and vnfA::lacZ fusions in A. vinelandii CARR was not inhibited by 1 mM Na 2 MoO 4 , whereas molybdenum at much lower concentration inhibited the expression of vnfH::lacZ and vnfA::lacZ fusions in A. vinelandii CA12. The mutant also exhibited normal acetylene reduction activity in the presence of 1 μM Na 2 MoO 4 . 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 Na 2 MoO 4 . 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 μM Na 2 MoO 4 , whereas A. vinelandii CA12 exhibited some activity even with 100 pM Na 2 MoO 4 .