LAUSR

The functional activity of different phylogenetic variants of the transcriptional activator of nitrogen fixation genes in the cells of root nodule bacteria (rhizobia) of different taxa was analyzed. For this purpose, recombinant strains of root nodule bacteria of the genera Mesorhizobium, Ensifer (Sinorhizobium), and Rhizobium were created using genetic engineering constructs based on the plasmid pJN105. This plasmid contains different phylogenetic variants of the nifA gene typical for bacteria of the genera Mesorhizobium, Ensifer, and Rhizobium under the control of the ParaBAD bacterial promoter. It was shown that in free-living recombinant cells of all three bacterial genera, the introduction of an additional active copy of the nifA gene to their genome resulted in emergence of detectable nitrogenase activity. The level of nitrogenase activity was not directly related to the phylogeny of the introduced nifA gene, which is most likely explained by the universality of the product of this gene within the studied group of bacteria. The data obtained indicate the possibility of combinatorial processes in the evolution of nitrogen fixation genes.