Identification and sequence of a nifJ-like gene in Rhodospirillum rubrum: partial characterization of a mutant unaffected in nitrogen fixation.
A nifJ-like gene was identified in the photosynthetic purple non-sulphur bacterium Rhodospirillum rubrum. A DNA segment hybridizing to Klebsiella pneumoniae nifJ was isolated, the gene was inactivated, and a mutant strain, SNJ-1, was constructed by allele replacement. The mutation was confirmed by DNA sequencing. Northern blotting and by the lack of pyruvate oxidoreductase activity. This is the first report of a nifJ-like gene in photosynthetic bacteria. Unexpectedly, SNJ-1 was capable of nitrogen fixation, and growth was similar to the wild-type strain under all conditions investigated. Therefore, this is also the first demonstration that a nifJ homologue, when present, is not essential for nitrogen fixation in a diazotroph. The nifJ-like gene was sequenced and found to have considerable similarity to published nifJ gene sequences from other organisms. By primer extension, the initiation site for transcription was located, and a typical sigma 54 promoter sequence was identified.
Lindblad
A
A
Department of Biochemistry, Arrhenius Laboratories for Natural Sciences, Stockholm University, Sweden.
Jansson
J
J
Brostedt
E
E
Johansson
M
M
Hellman
U
U
Nordlund
S
S
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics*; D001483:Base Sequence; D003001:Cloning, Molecular; D004269:DNA, Bacterial; D007658:Ketone Oxidoreductases / Q000737:chemistry / Q000235:genetics*; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009586:Nitrogen Fixation; D012247:Rhodospirillum rubrum / Q000201:enzymology* / Q000235:genetics; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid
D001426:Bacterial Proteins; D004269:DNA, Bacterial; D007658:Ketone Oxidoreductases; C039443:pyruvate-flavodoxin oxidoreductase