Figure 1.

Variation in the integration site of Stx phages and the Stx2 production level in STEC O145:H28 strains. The phylogenetic tree of 71 O145:H28 strains is shown in the left panel. The tree was constructed based on the recombination-free SNPs (3,347 sites) that were identified on the conserved chromosome backbone (3,851,013 bp) by RAxML using the GTR gamma substitution model. The reliabilities of the tree’s internal branches were assessed by bootstrapping with 1,000 pseudoreplicates. The bar in the upper-left corner indicates the mean number of nucleotide substitutions per site. Genome-finished strains are indicated by filled circles. Along with the tree, the geographic and ST/clade information of strains, the presence or absence of prophages at five loci, and the features of prophages are shown. In the right panel, the levels of MMC-induced Stx2 production by each strain are shown as the mean values with standard errors of biological triplicates. Note that the Stx2 production levels of eight stx2-positive strains whose genome sequences were obtained from NCBI were not determined.