FIG. 3.

Phylogenetic trees of stx₁ sequences (A) and stx₂ sequences (B) determined in this study and sequences of previously described stx genes and their variants. stx_1d and stx_2f were not included due to their considerable sequence divergence from classical stx₁ and stx₂, respectively. The horizontal bar indicates 0.001 (A) and 0.002 (B) nucleotide substitution per site. Reference DNA sequences for stx genes were obtained from GenBank and are identified in the phylogenetic trees by their accession numbers.