Kuznetsova I. G., Guro P. V., Chernikova N. V., Sazanova А. L., Sekste E. A., Tikhomirova N. Yu., Yakubov V. V., Belimov А. А., Safronova V. I., Karlov D. S.
Acta Biologica Sibirica 2026; 12: 1223–1247
The interaction of legume plants with nitrogen-fixing nodule bacteria (rhizobia) helps to enrich the soil with nutrients, thereby maintaining its fertility and ensuring the sustainability of pasture land scapes. In challenging soil and climatic conditions, the symbiotic relationship between legumes and rhizobia is of paramount importance. The study investigated the genetic diversity of endophytes of the order Hyphomicrobiales (Alfaproteobacteria) found in the nodules of endemic legumes O. exserta, O. evenorum, and O. ochotensis growing in Kamchatka (the Subarctic region of Russia). Forty strains were isolated from nodules, of which the largest number (17) were obtained from O. ochotensis, while 12 and 11 strains were isolated from O. evenorum and O. exserta, respectively. Microbial strains were iso lated using a standard method using mannitol-yeast nutrient agar (YMA). Primary taxonomic iden tification of strains was performed using ribosomal protein profiling and 16S rRNA gene sequencing. The largest number of strains were Mesorhizobium, Allobosea, and Tardiphaga. Isolates of the genera Rhizobium, Phyllobacterium, Arminella, and Pararhizobium were also present. Incubation tempera ture turned out to be a key factor in the selection of cultivable bacteria. Most Mesorhizobium and all Phyllobacterium were detected only at 28 °C, whereas Arminella, and Pararhizobium was found only at 15 °C. At 5 °C, no Mesorhizobium or Rhizobium isolates were obtained. A qualitative assessment of resistance to salt and hydrogen (pH) stress was carried out. A high diversity of pH stress tolerance was found among the strains studied. The widest pH range (4-10) was demonstrated by Mesorhizobium sp. RCAM07391, RCAM07494, P. myrsinacearum RCAM07525, RCAM07528, RCAM07530, and Rhizobium sp. RCAM07452, RCAM07474. Most strains could also grow at 3% NaCl concentration. Thus, this study expands our understanding of the biodiversity of cultivable bacteria associated with endemic legumes in subarctic regions. Rhizobial strains native to northern latitudes are of interest for further study of their symbiotic potential and adaptive properties, with a view to their potential use as microbial fertilizers for growing forage and pasture legumes in the extreme soil and climatic condi tions of Russia's Arctic and subarctic regions.
