Figure 1

A genome-scale estimate of phylogenetic relationships among species of Streptococcus. The tree topology is derived from the joint analysis of 504 single-copy gene sequences by using the BIONJ algorithm [55]. Each gene was comprised of exactly one sequence from each of the 12 genomes; the topology shown above is simplified to show only the relationships among the five nominal species of Streptococcus. The topology is unrooted, and branch lengths indicate the mean number of substitutions per codon, as inferred under codon model M0 [11].