COMPARISON OF 16S RIBOSOMAL-RNA GENES IN CLAVIBACTER-MICHIGANENSIS SUBSPECIES WITH OTHER CORYNEFORM BACTERIA

Nearly complete sequences (97-99%) of the 16S rRNA genes were determin ed for type strains of Clavibacter michiganensis subsp. michiganensis, Clavibacter michiganensis subsp. insidiosus, Clavibacter michiganensi s subsp. sepedonicus, and Clavibacter michiganensis subsp. nebraskensi s. The four subspecies had less than 1% dissimilarity in their 16S rRN A genes. Comparative studies indicated that the C. michiganensis subsp . shared relatively high homology with the 16S rRNA gene of Clavibacte r xyli. Further comparison with representatives of other Gram-positive coryneform and related bacteria with high G+C% values showed that thi s group of bacteria was subdivided into three clusters. One cluster co nsisted of the Clavibacter michiganensis subsp., Clavibacter xyli, Art hrobacter globiformis, Arthrobacter simplex, and Frankia sp.; another cluster consisted of members of the corynebacteria-mycobacteria-nocard ia (CMN) group of Mycobacteriaceae including Tsukamurella paur ometabo lum; and Propionibacterium freudenreichii alone formed a unique cluste r, which was remote from other coryneform bacteria analyzed. The three clusters may reflect a systematic rank higher than the genus level am ong these bacteria.