Ten mesorhizobial strains isolated from root-nodules of Anthyllis vulneraria by trapping using soils from southern France were studied to resolve their taxonomy. Their 16S rDNA sequences were identical and indicated that they are affiliated to the genus Mesorhizobium within the group M. prunaredense/M. delmotii/M. temperatum/M. mediterraneum/M. wenxiniae and M. robiniae as the closest defined species. Their evolutionary relationships with validated species were further characterized by multilocus sequence analysis (MLSA) using 4 protein-coding housekeeping genes (recA, atpD, glnII and dnaK), that divides the strains in two groups, and suggest that they belong to two distinct species. These results were well-supported by MALDI-TOF mass spectrometry analyses, wet-lab DNA-DNA hybridization (≤58%), and genome-based species delineation methods (ANI < 96%, in silico DDH < 70%), confirming their affiliation to two novel species. Based on these differences, Mesorhizobium ventifaucium (STM4922T = LMG 29643T = CFBP 8438T) and Mesorhizobium escarrei (type strain STM5069T = LMG 29642T = CFBP 8439T) are proposed as names for these two novel species. The phylogeny of nodulation genes nodC and nodA allocated the type strains into symbiovar anthyllidis as well as those of M. metallidurans STM2683T, M. delmotii STM4623T and M. prunaredense STM4891T, all recovered from the same legume species.
Keywords: Mesorhizobium sp. nov.; Phylogeny; Rhizobia; Symbiosis; Symbiovar; Taxonomy.
Copyright © 2022 Elsevier GmbH. All rights reserved.