Comparative genome analysis of deleted genes in Shigella flexneri 2a strain 301

Comparative genome analysis is performed between Shigella flexneri 2a strain 301 and its close relatives, the non-pathogenic E. coli K-12 strain MG1655. Result shows that there are 136 DNA segments whose size is larger than 1000 bp absent from Shigella flexneri 2a strain 301, which is up to 717253 bp in total length. These deleted segments altogether contain 670 open reading frames (ORFs). Prediction of these ORFs indicates that there are 40% genes of unknown function. The other genes of definite functions encode metabolic enzymes, structure proteins, transcription regulatory factors and some elements correlated with horizontal transfer. Here we compare the complete genomic sequences of the two closely related species, which differ in pathogenic phenotype. To our knowledge, this not only reveals the difference of genomic sequence between the two important enteric pathogens for the first time, but also provides valuable clues to further researches in its process of physiological activity, pathogenesis and the evolution of enteric bacteria.