Results and Discussion

All three strains possess a polar or subpolar flagellum and one approximately 500 kb plasmid. A BLAST similarity search revealed that all three isolates shared 99% identity with M. loti and M. ciceri according to their 16S rRNA gene. Distance matrix obtained using the nucleotide substitution rates (Knuc values) displayed the following values between the biserrula strains and representative members of the other genera: Bradyrhizobium > 11, Azorhizobium > 10, Agrobacterium > 7, Rhizobium > 7, Sinorhizobium > 4, Mesorhizobium < 2.6. Therefore the biserrula isolates were placed among the members of Mesorhizobium in the phylogenetic tree. The results of the physiological experiments and the symbiotic performance are also suggestive of a close relationship between biserrula bacteria and members of Mesorhizobium.

We have obtained five strains out of 88 field isolates that are completely different from the original inoculum strain according to their RPOl banding profiles. Further studies, involving DNA-hybridization, whole cell protein profiles and localization of the symbiotic genes, are being carried out to investigate the probable method of diversification of these bacteria in soil.

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