Molecular Phylogenetic Analysis of Salt-Tolerance-Related Genes in Root-Nodule Bacteria Species Sinorhizobium meliloti

Abstract

A molecular phylogenetic analysis of salt-tolerance-related genes was carried out using complete genome sequencing data available for 26 Sinorhizobium meliloti strains and for 25 bacterial strains belonging to 17 genera. It was revealed that the genes of the first and the second stages of the response to salt stress (aqpZ, trkH, and trkA, and betICBA) have copies of many of the above- indicated genes on pSymA. Data obtained can provide evidence that this replicon, known to be essential for nitrogen fixation rhizobia activity, also has a significant role in the formation of a stress-related gene pool. The closest putative phylogenetic relatives were identified for all 14 tested genes and these are the first insights into the evolutionary pathways for the formation of a stress-related gene pool in root nodule nitrogen-fixing bacteria.