The Molecular Differentiation of Renibacterjum Salmoninarumisolates

The nucleotide sequences of the rRNA genes and the 5' flanking region were determined for R. salmoninarumATCC 33209T from overlapping products generated by PCR amplification from the genomic DNA. Comparisonof the sequences with rRNA genes from a variety of bacteria demonstrated the close relatedness between R.salmoninarum and the high G+C group of the actinobacteria, in particular, Arthrobacter species. A regulatoryelement within the 5' leader of the rRNA operon was identical to an element, CL2, described for mycobacteria.PCR, DNA sequence analysis, and DNA hybridisation were performed to examine variation between isolates fromdiverse sources which represented the four 16S-23S rRNA intergenic spacer sequevars previously described for R.salmoninarum. Two 23S-5S rRNA intergenic spacer sequevars of identical length were found. DNA hybridisationusing probes complementary to 23S rDNA and 16S rDNA identified two rRNA operons which were identical ornearly identical amongst 40 isolates sourced from a variety of countries.Abbreviations: ITS 1, 16S-23S rRNAintergenic spacer; ITS2, 23S-5S rRNAintergenic spacer; SVsequevar,sequence variant