The variable genes identified with microarray in this study, mapped onto circular B. pertussis genome Tohama I. Variable genes not present in the Tohama I genome are not mapped in this figure. From the outside in, the outer circle 1 (blue) shows the position of the genes on the + strand. Circle 2 shows the COG functional categories on the + strand. The COG domains are color coded according to their main functional categories (for color code see additional file 8, Table S9). Circle 3 (red) indicates the position of the variable genes on the Tohama I genome. Circle 4 shows the GC % percentage of the Tohama I sequence.