Figure 4

dS / dN -based heatmap. The heatmap demonstrates a hierarchical cluster analysis of estimated dS/dN (the rate of synonymous to non-synonymous substitutions between taxa) of 1729 core genes from the 53 E. coli genomes. The differently colored labels designate phylogroups: D (light green), B2 (red), E (green), B1 (blue), and A (dark blue). Groups D, B2 and E consisted predominantly of pathogens; Group A was almost exclusively non-pathogenic, while Group B1 consisted of a mixture of pathogenic and non-pathogenic strains. The horizontal axis of the color key legend indicates multiples of dS to dN, where values close to 1 designates neutrality of selection.