Fig 3.

Proposed evolution of plasmid pO157-2 based on the stepwise evolution model for EHEC O157:H7. Possible acquisitions and/or losses of genes are indicated in branches. Clonal complexes (CCs) A3 to A7 are shown; changes predicted to have occurred: blue, gain of genes or regions; red, loss of genes or regions; gray, particular gene was truncated; green arrow, introduction of insertion sequence excision enhancer (IEE) in strains. Red circle, newly introduced CC A7 with plasmid pO157-2. Ancestral strain and plasmids A3 and A5 (shaded circles) have not been reported.