dnaJ and gyrB gene sequence relationship among species and strains of genus Streptococcus

The dnaJ and gyrB nucleotide sequences were determined for members of the genus Streptococcus. The average similarity between the species tested was 76.4% (69.7–100%) for dnaJ and 75.9 (70.1–98.7%) for gyrB. These data indicated that the dnaJ and gyrB genes are more divergent and more discriminatory than the 16S rDNA gene. Furthermore, the variation in the dnaJ nucleotide sequences among the mitis group was greater than that of the gyrB nucleotide sequences, especially between Streptococcus pneumoniae and Streptococcus mitis. Subsequently, the high discrimination power of dnaJ within the mitis group was confirmed. Thus, we conclude that the dnaJ and gyrB genes are efficient alternative targets for the classification of the genus Streptococcus, and that dnaJ is suitable for phylogenetic analysis of closely related Streptococcus strains.