Regulation of Nitrogen Fixation Genes in Rhizobium Meliloti

Rhizobium meliloti nif and fix genes are expressed in symbiotic conditions or in microaerobic cultures under the control of a cascade regulatory pathway. One regulon is activated by the oxygen sensitive activator NifA. The NifA independent regulon is activated by the Fnr homologue FixK. Both nifA and fixK are activated by the pair of regulatory proteins FixL and FixJ.