Mesorhizobium Ld1326N3 sp. nov, isolated from the root nodules of Lessertia diffusa
Three putative rhizobia strains were isolated from the root nodules of L. diffusa following a trapping experiment and identified to belong to the Mesorhizobium genus following 16S rRNA sequence analyses. The three Mesorhizobium strains were taxonomically interrogated through a genealogical concordance approach based on the maximum-likelihood phylogenies of five protein-coding gene regions (recA, atpD, dnaK, rpoB, and gyrB), where they formed a congruent group in all single-gene phylogenies, unique from described Mesorhizobium type strains. Further characterization of the strains included a multi-locus sequence analysis (MLSA) phylogeny and various phenotypic tests which broadly supported the grouping of the strains. Additional support for the potential novelty of this congruent group was provided through genome-based data and included average nucleotide identity (ANI) which demonstrated less than 91% similarity between the putative novel species and close relative Mesorhizobium type strains. The type strain, Ld1326N3T, was able to form effective nodules on L.diffusa plants, within which the bacteria could fix nitrogen for the host plant. The genealogical concordant group is proposed to be a novel species Mesorhizobium subsalinum sp. nov. with Ld1326N3T as its type strain.