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Figure 1 | BMC Genomics

Figure 1

From: M-protein and other intrinsic virulence factors of Streptococcus pyogenes are encoded on an ancient pathogenicity island

Figure 1

Cumulative GC skew (A) and TA skew (B) of the chromosome of the M1 S. pyogenes SF370. Cumulative skews (Y-axis, in nucleotide kilosteps) are represented along the chromosome (X-axis). Both skews are performed on one of the two strand of the streptococcal DNA double helix. The TA skew (B) reveals segments with steeper slopes referred to as steep-slope segments (SSRs) and revealing regions with different nucleotide composition. Phagic SSRs are represented by grey rectangles and numbered as they appear on the chromosome, while the conserved non-phagic SSR is outlined by a boxed orange rectangle. Virulence genes (blue dots) are spotted according to their position on the chromosome and the distance to the next virulence gene (right Y-axis, logarithmic scale). The overall average distance between virulence genes is 54.8 kb, except for a group of 10 genes (circled) present in the non-phagic 47-kb SSR for which the average distance is only 4.3 kb. This represents a ten-fold greater concentration of virulence factors compared to the rest of the chromosome.

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