Mesorhizobium carmichaelinearum sp. nov., isolated from Carmichaelineae spp. root nodules

Abstract

Five strains of Gram-stain-negative, rod-shaped bacteria were isolated from Carmichaelia and Montigena root nodules. Based on 16S rRNA gene phylogeny, they were shown to belong to the genus Mesorhizobium , and to be most closely related to Mesorhizobium jarvisii ATCC 33669ᵀ(100–99.6 % sequence similarity), Mesorhizobium huakuii IAM 14158ᵀ (99.9–99.6 %), Mesorhizobium japonicum MAFF303099ᵀ(99.8–99.6 %) and Mesorhizobium erdmanii USDA 3471ᵀ(99.8–99.5 %). Additionally, the strains formed distinct groups based on housekeeping gene analysis and were most closely related to M. jarvisii ATCC 33669T (89.6–89.5 and 97.6–97.3 % sequence similarity for glnII and recA, respectively), M. erdmanii USDA 3471ᵀ (94.3–94.0 and 94.9–94.1 %), M. japonicum MAFF303099ᵀ(90.0–89.9 and 96.7–96.2 %) and M. huakuii IAM 14158ᵀ (89.9–90.0 and 95.4–94.9 %). Chemotaxonomic data supported the assignment of the strains to the genus Mesorhizobium and DNA–DNA hybridizations, average nucleotide identity analysis, matrix-assisted laser desorption ionization time-of-flight MS analysis, physiological and biochemical tests differentiated them genotypically and phenotypically from their nearest neighbouring species. Therefore, these strains are considered to represent a novel species, for which the name Mesorhizobium carmichaelinearum sp. nov. is proposed. The type strain is ICMP 18942ᵀ(=MonP1N1ᵀ=LMG 28414ᵀ).