Analysis of symbiotic genes of leguminous root nodule bacteria grown in the southern urals.

Bacterial strains isolated from the nodules, tissues, and root surface of wild legumes growing in the Southern Urals related to the tribes Galegeae, Hedysareae, Genisteae, Trifolieae, and Loteae were examined for the presence in their genomes of symbiotic ( sym) genes. It was found that the sym-genes are present in microorganisms isolated only from the nodules of the analyzed plants ( sym strains). Phylogenetic analysis of sym strains on the basis of a comparative analysis of 16S rRNA gene sequences showed that sym strains belong to five families of nodule bacteria: Mesorhizobium, Bradyrhizobium, Sinorhizobium, Rhizobium, and Phyllobacterium. A study the phylogeny of the sym-genes showed that the nodule bacteria of leguminous plants of the Southern Urals at the genus level are mainly characterized by a parallel evolution of symbiotic genes and the 16S rRNA gene. Thus, cases of horizontal transfer of sym genes, which sometimes leads to the formation of certain types of atypical rhizobial strains of leguminous plants, are detected in nodule bacteria populations. [ABSTRACT FROM AUTHOR]