Phyllobacterium zundukense sp. nov., a novel species of rhizobia isolated from root nodules of the legume species Oxytropis triphylla (Pall.) Pers.

Abstract

Gram-negative strains Tri-36, Tri-38, Tri-48^T and Tri-53 were isolated from root nodules of the relict legume Oxytropis triphylla (Pall.) Pers. originating from Zunduk Cape (Baikal Lake region, Russia). 16S rRNA gene sequencing showed that the novel isolates were phylogenetically closest to the type strains Phyllobacterium sophorae LMG 27899^T, Phyllobacterium brassicacearum LMG 22836^T, Phyllobacterium endophyticum LMG 26470^T and Phyllobacterium bourgognense LMG 22837^T while similarity levels between the isolates and the most closely related strain P. endophyticum LMG 26470^T were 98.8-99.5 %. The recA and glnII genes of the isolates showed highest sequence similarities with P. sophorae LMG 27899^T (95.4 and 89.5 %, respectively) and P. brassicacearum LMG 22836^T (91.4 and 85.1 %, respectively). Comparative analysis of phenotypic properties between the novel isolates and the closest reference strains P. sophorae LMG 27899^T, P. brassicacearum LMG 22836^T and P. endophyticum LMG 26470^T was performed using a microassay system. Average nucleotide identities between the whole genome sequences of the isolates Tri-38 and Tri-48^T and P. sophorae LMG 27899^T, P. brassicacearum LMG 22836^T and P. endophyticum LMG 26470^T ranged from 79.23 % for P. endophyticum LMG 26470^T to 85.74 % for P. sophorae LMG 27899^T. The common nodABC genes required for legume nodulation were absent from strains Tri-38 and Tri-48^T, although some other symbiotic nod and fix genes were detected. On the basis of genotypic and phenotypic analysis, a novel species, Phyllobacterium zundukense sp. nov. (type strain Tri-48^T=LMG 30371^T=RCAM 03910^T), is proposed.