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

Junping Peng,Meisheng Sun,Wen Bin,Jian Yang,Xiaobing Zhang,E Yang,Jing Wang,Candong Wei,Qi Jin

doi:10.1186/1471-2164-7-218

Abstract

BackgroundCompelling evidence indicates that Shigella species, the etiologic agents of bacillary dysentery, as well as enteroinvasive Escherichia coli, are derived from multiple origins of Escherichia coli and form a single pathovar. To further understand the genome diversity and virulence evolution of Shigella, comparative genomic hybridization microarray analysis was employed to compare the gene content of E. coli K-12 with those of 43 Shigella strains from all lineages.ResultsFor the 43 strains subjected to CGH microarray analyses, the common backbone of the Shigella 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.ConclusionThese results support the hypothesis that by gain and loss of functions, Shigella 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.

Highlights

Compelling evidence indicates that Shigella species, the etiologic agents of bacillary dysentery, as well as enteroinvasive Escherichia coli, are derived from multiple origins of Escherichia coli and form a single pathovar
Analysis of control hybridizations indicates the level of sensitivity of the microarray Results for the four sequenced Shigella strains' hybridization were directly compared to expected hybridization results as assessed by the percent identity of each MG1655 and Shigella amplicon to the four sequenced Shigella genome sequences
Genome order analysis of E. coli dataset reveals discrete regions among Shigella serotypes Generally, the results of the comparative genomic hybridization (CGH) demonstrated that the genome contents of Shigella spp. isolates differ markedly from that of E. coli strain MG1655

Summary

Introduction

Compelling evidence indicates that Shigella species, the etiologic agents of bacillary dysentery, as well as enteroinvasive Escherichia coli, are derived from multiple origins of Escherichia coli and form a single pathovar. Gram-negative, facultative anaerobes of the genus Shigella, the principal etiologic agents of bacillary dysentery, continue to pose a threat to public health, with an estimated annual incidence of 164.7 million and 1.1 million deaths worldwide [1]. They are sub-grouped into four species: Shigella dysenteriae, Shigella flexneri, Shigella boydii and Shigella sonnei. The results of multilocus enzyme electrophoresis and multilocus sequence typing (MLST) argue that Shigella diverged from Escherichia coli in eight independent events and, may not constitute a separate genus [2,3] These results can't reflect the influence of horizontal gene transfer and gene loss. Comparison of genomic differences between different flora and strains will be helpful in revealing gene acquisition and gene loss in bacteria genome evolution, and in revealing the genetic basis of the diversity of biological activities [4]

Methods

Results

Discussion

Conclusion