The use of comparative genomic hybridization to characterize genome dynamics and diversity among the serotypes of Shigella

Abstract

<p>Abstract</p> <p>Background</p> <p>Compelling evidence indicates that <it>Shigella </it>species, the etiologic agents of bacillary dysentery, as well as <it>enteroinvasive Escherichia coli</it>, are derived from multiple origins of <it>Escherichia coli </it>and form a single pathovar. To further understand the genome diversity and virulence evolution of <it>Shigella</it>, comparative genomic hybridization microarray analysis was employed to compare the gene content of <it>E. coli </it>K-12 with those of 43 <it>Shigella </it>strains from all lineages.</p> <p>Results</p> <p>For the 43 strains subjected to CGH microarray analyses, the common backbone of the <it>Shigella </it>genome was estimated to contain more than 1,900 open reading frames (ORFs), with a mean number of 726 undetectable ORFs. The mosaic distribution of absent regions indicated that insertions and/or deletions have led to the highly diversified genomes of pathogenic strains.</p> <p>Conclusion</p> <p>These results support the hypothesis that by gain and loss of functions, <it>Shigella </it>species became successful human pathogens through convergent evolution from diverse genomic backgrounds. Moreover, we also found many specific differences between different lineages, providing a window into understanding bacterial speciation and taxonomic relationships.</p