Partial sequence comparison of the rpoB, sodA, groEL and gyrB genes within the genus Streptococcus

Phylogenetic analysis and species identification of members of the genus Streptococcus were carried out using partial sequence comparison of the 16S rRNA gene (1468-1478 bp), rpoB, encoding the beta subunit of RNA polymerase (659-680 bp), sodA, encoding the manganese-dependent superoxide dismutase (435-462 bp), groEL, encoding the 60 kDa heat-shock protein (757 bp), and gyrB, encoding the Beta subunit of DNA gyrase (458-461 bp). For the first time, most species within the genus Streptococcus were represented in the study (65 strains, representing 58 species and nine subspecies). Phylogenies inferred from rpoB, sodA, gyrB and groEL sequence comparisons were more discriminative than those inferred from 16S rRNA gene sequence comparison, and showed common clusters. The minimal interspecies divergence was 0.3, 2.7, 0, 2.5 and 3.4 % for the 16S rRNA gene, rpoB, sodA, gyrB and groEL, respectively. In general, groEL partial gene sequence comparison represented the best tool for identifying species and subspecies and for phylogenetic analysis.