Comparative genomics and phylogenetic analysis of S. dysenteriae subgroup

Genomic compositions of representatives of thirteen S. dysenteriae serotypes were investigated by performing comparative genomic hybridization (CGH) with microarray containing the whole genomic ORFs (open reading frames, ORFs) of E. coli K12 strain MG1655 and spe-cific ORFs of S. dysenteriae A1 strain Sd51197. The CGH results indicated the genomes of the serotypes contain 2654 conserved ORFs originating from E. coli. However, 219 intrinsic genes of E. coli including those prophage genes, molecular chaperones, synthesis of specific O antigen and so on were absent. Moreover, some specific genes such as type II secretion system associ-ated components, iron transport related genes and some others as well were acquired through horizontal transfer. According to phylogenic trees based on genetic composition, it was demon-strated that A1, A2, A8, A10 were distinct from the other S. dysenteriae serotypes. Our results in this report may provide new insights into the physiological process, pathogenicity and evolution of S. dysenteriae.