The taxonomy of rhizobia is in a state of flux. Since the first description of the genus Rhizobium to accommodate root and/or stem-nodule bacteria by Frank (1889), there have been a number of revisions to its description and the addition of many novel species. At the time of writing, the genus Rhizobium comprises 43 recognized species Species of the genus Rhizobium have traditionally been considered as legume endosymbionts and have generally been isolated from nodules on leguminous plants. More recently, novel species of this genus have also been found in different environments,such as Rhizobium selenitireducens and Rhizobium daejeonense isolated from bioreactors , Rhizobium cellulosilyticum from
sawdust of Populus alba ,Rhizobium oryzae from wild rice and strains of Rhizobium alamii from the rhizosphere of sunflowers A novel bacterial strain, J3-A127T, isolated during the course of studies of the bacterial diversity in rice (Oryza sativa) roots, was studied using a polyphasic taxonomic approach. It is proposed that this strain represents a novel species of the genus Rhizobium.