Figure 3
Neighbor-joining tree of full-length polymorphism-derived genotypes. The triplicate sets of numbers on the tree represent bootstrap values from neighbor-joining, parsimony, and maximum-likelihood algorithms, respectively. Outer taxonomic unit genotype numbers correspond with genotype sequences recorded in Additional data file 3. The outer taxonomic units are color coded by genotype for the tir 255 T>A polymorphism and host origin. Roman numerals depict two subclades that account for 92% of the human STEC O157 strains genotyped in this study. The scale bar represents substitutions per site.