CLASSIFICATION OF AUSTRIAN RHIZOBIA AND THE MEXICAN ISOLATE FL27 OBTAINED FROM PHASEOLUS-VULGARIS L. AS RHIZOBIUM-GALLICUM

The phylogenetic positions of four rhizobial strains obtained from nod ules of common bean plants (Phaseolus vulgaris L.) grown in an Austria n soil and of the Mexican bean isolate FL27 are described. Analysis of the 16S rRNA genes revealed sequences almost identical to that of the Rhizobium gallicum type strain, R602sp, with a maximum of two nucleot ide substitutions. Comparison of the 16S rRNA gene sequences with thos e from other bacteria indicated highest similarity to Rhizobium sp. st rain OK-50, Rhizobium leguminosarum IAM 12609, and Rhizobium etli. DNA homology determined by DNA-DNA hybridization was high among the Austr ian isolates and R602sp(T) (45 to 90%) and ranged from 21 to 65% with FL27, but hybridization analysis revealed very low homology to the rec ognized common bean-nodulating species, R. leguminosarum by. phaseoli, R. etli, and Rhizobium tropici. Ribosomal gene organization was studi ed by Southern hybridization with the 16S rRNA gene and temperature gr adient gel electrophoresis, indicating identical organizations and the presence of three identical 16S rRNA copies in the genome of this spe cies. The six strains investigated showed different plasmid profiles b ased on their geographical origins. We propose that the Austrian isola tes and the Mexican strain FL27 are members of the species R. gallicum .