Bradyrhizobium guangdongense sp. nov. and Bradyrhizobium guangxiense sp. nov., isolated from effective nodules of peanut

Abstract

Seven slow-growing rhizobia isolated from effective nodules of Arachis hypogaea were assigned to the genus Bradyrhizobium based on sharing 96.3–99.9 % 16S rRNA gene sequence similarity with the type strains of recognized Bradyrhizobium species. Multilocus sequence analysis of glnII, recA, gyrB and dnaK genes indicated that the seven strains belonged to two novel species represented by CCBAU 51649T and CCBAU 53363T. Strain CCBAU 51649T shared 94, 93.4, 92.3 and 94.9 % and CCBAU 53363T shared 91.4, 94.5, 94.6 and 97.7 % sequence similarity for the glnII, recA, gyrB and dnaK genes, respectively, with respect to the closest related species Bradyrhizobium manausense BR 3351T and Bradyrhizobium yuanmingense CCBAU 10071T. Summed feature 8 and C16 : 0 were the predominant fatty acid components for strains CCBAU 51649T and CCBAU 53363T. DNA–DNA hybridization and analysis of phenotypic characteristics also distinguished these strains from the closest related Bradyrhizobium species. The strains formed effective nodules on Arachis hypogaea, Lablab purpureus and Aeschynomene indica, and they had identical nodA genes to Bradyrhizobium sp. PI237 but were phylogenetically divergent from other available nodA genes at less than 66 % similarity. Based in these results, strains CCBAU 51649T ( = CGMCC 1.15034T = LMG 28620T) and CCBAU 53363T ( = CGMCC 1.15035T = LMG 28621T) are designated the type strains of two novel species, for which the names Bradyrhizobium guangdongense sp. nov. and Bradyrhizobium guangxiense sp. nov. are proposed, respectively.