Rhizobium mesosinicum sp nov., isolated from root nodules of three different legumes

Thirteen novel strains were isolated from root nodules of three different leguminous plants of the genera Albizia, Kummerowia and Dalbergia grown in China. Cells of these strains were Gram-negative, strictly aerobic, non-spore-forming, motile rods. Phylogenetic analysis of 16S rRNA gene sequences revealed that they belong to the genus Rhizobium. A representative strain, CCBAU 25010(T), showed 98.8 % 16S rRNA gene sequence similarity to its closest phylogenetic relative, Rhizobium sullae IS123(T). The 16S-23S intergenic spacer (ITS) sequence of CCBAU 25010(T) shared 91.5 and 87.2% sequence similarity, respectively, with those of Rhizobium etli CFN 42(T) and Rhizobium, leguminosarum LMG 14904(T). Analysis of the sequences of the housekeeping genes atpD and recA was in agreement with the results of ITS sequence analysis. The nodC gene sequence of CCBAU 25010(T) was identical to that of Rhizobium tropici CFN 299. DNA-DNA hybridization values for strain CCBAU 25010 T ranged from 20.7 % (with Rhizobium mongolense USDA 1844(T)) to 34.4 % (with R. leguminosarum USDA 2370(T)). Cell protein SDS-PAGE, BCX-PCR and several phenotypic characteristics, such as use of sole carbon sources and antibiotic resistance, could differentiate the novel strains from defined Rhizobium species. We therefore propose that the novel strains reported in this study form a novel species, Rhizobium mesosinicum sp. nov., with the type strain CCBAU 25010(T) (=LMG 24135(T) =JCM 14777(T).)