[Study on polyphasic taxonomy of rhizobia isolated from Lespedeza species]

The diversity of rhizobia isolated from Lespedeza spp. was determined on the basis of numerical analysis of phenotypic characteristics, sodium dodecyl sulfate-polyacrylarmide gel electrophoresis (SDS-PAGE) of proteins, DNA-DNA homology and restriction fragment length polymorphism (RFLP) analysis of 16S-ribosomal DNA genes. According to numerical analysis of 125 phenotypic characteristics, strains were divided into two groups at a similarity level of 67%. Group I included all the fast-growing strains, group II included all the slow-growing strains. Above the similarity level of 80%, four subgroups could be further divided. Subgroup I was fast-growing rhizobia containing representative strain of Sinorhizobium saheli. Subgroup II, III, IV were slow-growing rhizobia. Subgroup II composed of strains isolated from Lespedeza cuneata in Beijing area and these isolates produced acid in medium containing mannitol. Subgroup III included type strain of Bradyrhizobium japonicum. The DNA G + C contents and DNA-DNA homology of the members of above four subgroups were determined. The subgroup I shared the same DNA homologous group with S. saheli, subgroup III belonged to B. japonicum, subgroup IV belonged to B. elkanii, subgroup II was an unique DNA homologous group which showed low level of DNA relatedness with other slow-growing rhizobia species. RFLP analysis of 16S rDNA genes verified that the subgroup II was a distinctive genealine and showed genetic variation within the strains in it.