Rhizobium puerariae sp. nov., an endophytic bacterium from the root nodules of the medicinal plant Pueraria candollei var. candollei

A Gram-stain-negative, rod-shaped, motile bacterium, PC004T, was isolated from root nodules of the Thai medicinal plant Pueraria candollei var. candollei. 16S rRNA gene sequence analysis indicated that the strain is phylogenetically related to species in the genus Rhizobium, showing highest similarity (96.6 %) with Rhizobium mesosinicum HAMBI 3194T. The phylogenetic tree reconstructed based on 16S rRNA gene sequences showed that strain PC004T forms a cluster with Rhizobium petrolearium KCTC 23288T. Based on atpD, gyrB and recA gene sequences, strain PC004T also showed low similarity ( < 90 %) to reference strains. These phylogenetic data indicate that PC004T may represent a novel species. Strain PC004T also exhibited low DNA–DNA relatedness with R. mesosinicum HAMBI 3194T (8.2 %) and R. petrolearium KCTC 23288T (26.3 %). The DNA G+C content of strain PC004T was 64 mol%, which is within the range reported for the genus Rhizobium. The major fatty acid of PC004T was C18 : 1ω7c with minor amounts of C16 : 0, C16 : 0 3-OH, C18 : 0 3-OH, C18 : 1 2-OH, C19 : 0 cyclo ω8c and summed feature 2. The strain was able to grow at pH 12 and with up to 2 % (w/v) NaCl. Strain PC004T did not nodulate five tested legumes and the nifH and nodC genes were not detected by PCR. Based on the physiological, chemotaxonomic and phenotypic data from this study, strain PC004T represents a novel species of the genus Rhizobium, for which the name Rhizobium puerariae sp. nov. is proposed; the type strain is PC004T ( = BCC 73740T = NBRC 110722T).