MOLECULAR RELATIONSHIP OF AN ATYPICAL AZOSPIRILLUM STRAIN 4T TO OTHERAZOSPIRILLUM SPECIES

DNA/DNA hybridization, plasmid content and partial 16S rDNA sequence w ere determined to confirm the relationship between two Azospirillum st rains, 4B and 4T, isolated from the same rice rhizosphere. The partial 16S rDNA sequence was determined for 9 strains belonging to 5 Azospir illum species which included Azospirillum lipoferum strains 4B and 4T, and was compared to a set of ribosomal sequences from other bacteria of the alpha subdivision of the Proteobacteria. Four Azospirillum spec ies sequences were found to form a coherent group, whereas A. haloprae ferens was found to be more divergent. The five Azospirillum species w ere closely related to Magnetos pirillum and to a lesser extent to Rho dospirillum, with which they share some morphological features. The pa rtial 16S rDNA sequences of the two strains 4B and 4T were identical a nd confirmed the closeness of these two strains. Plasmid content and D NA/DNA hybridization data (S1 nuclease and Delta Tm) grouped Azospiril lum strains 4B and 4T with the other strains of species Azospirillum l ipoferum (USA5a, 59b, BR17). Other biochemical and genetic characters confirmed the grouping of Azospirillum strains 4B and 4T together with A. lipoferum.