Mesorhizobium waimense sp. nov. isolated from Sophora longicarinata root nodules and Mesorhizobium cantuariense sp. nov. isolated from Sophora microphylla root nodules

Abstract

In total 14 strains of Gram-stain-negative, rod-shaped bacteria were isolated from Sophora longicarinata and Sophora microphylla root nodules and authenticated as rhizobia on these hosts. Based on the 16S rRNA gene phylogeny, they were shown to belong to the genus Mesorhizobium, and the strains from S. longicarinata were most closely related to Mesorhizobium amorphae ACCC 19665ᵀ (99.8–99.9 %), Mesorhizobium huakuii IAM 14158ᵀ (99.8–99.9 %), Mesorhizobium loti USDA 3471ᵀ (99.5–99.9 %) and Mesorhizobium septentrionale SDW 014ᵀ (99.6–99.8 %), whilst the strains from S. microphylla were most closely related to Mesorhizobium ciceri UPM-Ca7ᵀ (99.8–99.9 %), Mesorhizobium qingshengii CCBAU 33460ᵀ (99.7 %) and Mesorhizobium shangrilense CCBAU 65327ᵀ (99.6 %). Additionally, these strains formed two distinct groups in phylogenetic trees of the housekeeping genes glnII, recA and rpoB. Chemotaxonomic data, including fatty acid profiles, supported the assignment of the strains to the genus Mesorhizobium and allowed differentiation from the closest neighbours. Results of DNA–DNA hybridizations, MALDI-TOF MS analysis, ERIC-PCR, and physiological and biochemical tests allowed genotypic and phenotypic differentiation of our strains from their closest neighbouring species. Therefore, the strains isolated from S. longicarinata and S. microphylla represent two novel species for which the names Mesorhizobium waimense sp. nov. (ICMP 19557ᵀ = LMG 28228ᵀ = HAMBI 3608ᵀ) and Mesorhizobium cantuariense sp. nov. (ICMP 19515ᵀ = LMG 28225ᵀ = HAMBI 3604ᵀ), are proposed respectively.