Rhizobium brockwellii sp. nov., Rhizobium johnstonii sp. nov. and Rhizobium beringeri sp. nov., three genospecies within the Rhizobium leguminosarum species complex
J. Peter W. Young, Beatriz Jorrín, Sara Moeskjær, Euan K. James
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 CC275e T =LMG 6122 T = ICMP 2163 T =NZP 561 T = PDDCC 2163 T =HAMBI 13 T ), Rhizobium johnstonii sp. nov. (gsB, 54 strains, type strain 3841 T = LMG 32736 T =DSM 114642 T ) and Rhizobium beringeri sp. nov. (gsD, 8 strains, type strain SM51 T = LMG 32895 T = DSM 115206 T ). 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.