Figure 4

The E. coli strain phylogeny inferred based on (a) the prpB gene sequences is different from the more reliable phylogeny inferred based on (b) the concatenated sequences of 100 randomly selected genes. For each of the two trees, bootstrap analysis was applied using 1,000 replicas. The number of replicas that agree with each branch assignment is indicated. Unlike in the 'true' tree represented in Figure 1 and in (b), the prpB-tree shows the EHEC strains, E. coli O157:H7 and E. coli O157:H7 EDL933 to be closer to E. coli UTI89 and E. coli APEC 01 than to the lab strains of E. coli. This may indicate that the prpB was horizontally transferred into the EHEC strains.