Differences in rate substitution among yaaW sequences. Number of mutations exclusive of group A sequences (m1 mutations) versus number of exclusive mutations of group B sequences (m2 mutations) in yaaW genes in windows of 102 nucleotides. X values denotes the mid position of each window in E. coli yaaW sequence. Contiguous windows overlap 51 nucleotides. Thick lines denote the mean number of exclusive mutations for m1 and m2 changes. Dashed lines indicated the number of m1 and m2 changes for sequences showing the most extreme values. Each point is accompanied by its standard deviation.