ISSN:
1365-2958
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Biology
,
Medicine
Notes:
The nucleotide sequence of a 1 kb fragment upstream of Azorhizobium caulinodans fixL was established. An open reading frame of 744 bp was identified as a fixK homologue. A kanamycin cartridge was inserted into the cloned fixK-1ike gene and recombined Into the host genome. The resulting mutant was Nif− Fix− suggesting that FixK was required for nitrogen fixation both in symbiotic conditions and in the free-living state. Using a pfixK–lacZ fusion, the FixLJ products were shown to control the expression of fixK. Using a pnifA–lacZ fusion, the FixK product was shown to regulate positively the transcription of nifA in bacteria grown in the free-living state. In addition, a double ntrC–fixL mutant was constructed and was shown to be completely devoid of nitrogenase activity. A model of regulation, based on these data, is presented and might explain the unusual ability of A. caulinodans to fix nitrogen both under symbiotic conditions and in the free-living state.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1111/j.1365-2958.1991.tb00820.x
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