Open AccessPhysiological characterisation of an Azotobacter vinelandii nifU ‐deletion mutant and its spontaneous Nif + revertants that over‐produce cytochrome bd
Author(s) -
Hill Susan,
He Luhong,
Kennedy Christina
Publication year - 1999
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.1574-6968.1999.tb13618.x
Subject(s) - azotobacter vinelandii , mutant , nitrogenase , cytochrome , mutation , chemistry , microbiology and biotechnology , biology , biochemistry , enzyme , genetics , gene , bacteria , nitrogen fixation
Abstract A nifU ‐deletion mutant of Azotobacter vinelandii fixed N 2 , but only under low atmospheric O 2 (2 kPa), whereas, under air, it reverted to Nif + at 5×10 −8 . The revertant's O 2 ‐tolerant nitrogenase activity, surprisingly, was not accompanied by an increased respiration rate, although, like cydR mutants, the revertants over‐produce cytochrome bd . The introduction of a cydR mutation into the nifU mutant yielded transformants, of which 100% fixed N 2 in air. This is consistent with the revertant mutations residing in cydR . Inactivation of CydR (a Fnr‐like transcriptional repressor) could lead to the up‐regulation of a process (e.g. IscU activity in i ron‐ s ulfur c luster formation) that substitutes for NifU.