Figure 4. Unrooted Bayesian tree of the concatenated sequence of the 92 sequence types (STs) of Streptococcus suis. The tree was constructed by using MrBayes (version 3.1.1) according to the HKY85 model of DNA substitution with no rate variation across sites. Four Markov chains were run for a million generations, and the Markov chain is sampled every 100 generations (18). The sampled parameter values were summarized by discarding the first 2,000 samples as burn-in. On the basis of the last 9,000 samples taken from the posterior probability distribution, a 50% majority rule consensus tree was computed. The posterior probability given on each branch is a percentage of these trees supporting each node. The 6 lineages defined in this study are shadowed in light gray. The 6 major clonal complexes identified previously by King et al. (8) as well as in this study are shadowed in dark gray. The five STs containing isolates from human invasive disease are shown as red dots.