FIG. 1.

Phylogenetic tree determined on the basis of the sequences of the ITS regions of 11. S. mitis (Smit) strains, 11 S. oralis (Soral) strains, and 17 S. pneumoniae (Spneu) strains obtained by the unrooted neighbor-joining method in the MEGA (version 4.0) program package. The scale bar indicates the evolutionary distance between the sequences determined by calculation of the percent sequence divergence. It clearly demonstrates that S. mitis, S. pneumoniae, and S. oralis are genetically closely related species and cannot be discriminated from each other on the basis of the sequences of their ITS regions.