Figure 2.

Phylogenetic tree analysis of the stx gene sequences and the DNA sequence of the corresponding pR’ fragments. The phylogenetic tree was based on 26 sequences from 17 STEC strains (Table 1). Neighbor-Joining trees were generated in Geneious using the Tamura–Nei model. The reliabilities of the internal branches were assessed using bootstrapping with 1000 pseudo-replicates. The scale bars represent the number of the substitution per site. Bootstrap values over 70% are displayed. Shigella dysenteriea type 1 strain Sd197 was included as the outgroup. Strains that had significant phylogenetic differences between the pR’ region and stx gene are highlighted by dots and were used in downstream studies. (A) Phylogenetic tree generated by comparing the stx genes, which included both subunit A and B. (B) Phylogenetic tree generated by aligning the pR’ region located between Q and stx.