Rhizobium brockwellii sp. nov., Rhizobium johnstonii sp. nov. and Rhizobium beringeri sp. nov., three genospecies within the Rhizobium leguminosarum species complex

Abstract

Genomic evidence indicates that the Rhizobium leguminosarum species complex comprises multiple distinct species, perhaps 18 or more. Of the five earliest genospecies (gs) to be described, only two have formal names: R. leguminosarum sensu stricto (gsE) and Rhizobium ruizarguesonis (gsC). Here, we provide formal descriptions and names for the other three genospecies, based on the publicly available genome sequences for multiple strains of each species: Rhizobium brockwellii sp. nov. (gsA, 37 strains, type strain CC275eT=LMG 6122T = ICMP 2163T=NZP 561T = PDDCC 2163T=HAMBI 13T), Rhizobium johnstonii sp. nov. (gsB, 54 strains, type strain 3841T = LMG 32736T=DSM 114642T) and Rhizobium beringeri sp. nov. (gsD, 8 strains, type strain SM51T = LMG 32895T = DSM 115206T). Each species forms a well-supported clade in a phylogeny based on 120 concatenated core genes. All strains have average nucleotide identity (ANI) above 96 % with the relevant type strain and below 96 % with all other type strains. Each species is characterised by a number of genes that are absent or rare in other species.