Mesorhizobium calcicola sp. nov., Mesorhizobium waitakense sp. nov., Mesorhizobium sophorae sp. nov., Mesorhizobium newzealandense sp. nov. and Mesorhizobium kowhaii sp. nov. isolated from Sophora root nodules

Abstract

In total, 31 strains of Gram-stain-negative, rod-shaped bacteria were isolated from Sophora root nodules and authenticated as rhizobia on this host. Based on 16S rRNA gene phylogeny, they were shown to belong to the genus Mesorhizobium, with the representative strains ICMP 19560ᵀ, ICMP 19523ᵀ, ICMP 19535ᵀ, ICMP 19545ᵀ and ICMP 19512ᵀ being related most closely to Mesorhizobium sangaii SCAU7ᵀ (99.9–99.6 % similarity), Mesorhizobium cantuariense ICMP 19515ᵀ (99.7–99.6 %) and Mesorhizobium ciceri UMP-CA7ᵀ (99.7–99.5 %). Additionally, the novel strains formed distinct groups based on housekeeping gene sequence analysis and were closely related to Mesorhizobium waimense ICMP 19557ᵀ (93.5–94.9, 92.5–95.6 and 94.2–96.0 %), M. cantuariense ICMP 19515ᵀ (93.1–97.7, 93.5–95.4 and 94.8–96.8 %) and M. ciceri UMP-CA7ᵀ (93.2–97.2, 94.6–96.8 and 95.5–97.3 %) for glnII, recA and rpoB, respectively. Chemotaxonomic data supported the assignment of the strains to the genus Mesorhizobium, and DNA–DNA hybridizations, matrix-assisted laser desorption/ionization time-of-flight MS analysis, enterobacterial repetitive intergenic consensus PCR, physiological and biochemical tests allowed the genotypic and phenotypic differentiation from their nearest neighbouring species. Therefore, these strains represent five novel species for which the names Mesorhizobium calcicola sp. nov. (type strain ICMP 19560ᵀ = LMG 28224ᵀ = HAMBI 3609ᵀ), Mesorhizobium waitakense sp. nov. (type strain ICMP 19523ᵀ = LMG 28227ᵀ = HAMBI 3605ᵀ), Mesorhizobium sophorae sp. nov. (type strain ICMP 19535ᵀ = LMG 28223ᵀ = HAMBI 3606ᵀ), Mesorhizobium newzealandense sp. nov. (type strain ICMP19545ᵀ = LMG 28226ᵀ = HAMBI 3607ᵀ) and Mesorhizobium kowhaii sp. nov. (type strain ICMP 19512ᵀ = LMG 28222ᵀ = HAMBI 3603ᵀ) are proposed.