The Genetic Organization & Transcriptional Regulation of Shigella Virulence Genes


William D. Picking, Wendy L Picking (Eds.)

Document Type

Book Section

Publication Date


Publication Title

Shigella: the Molecular and Cellular Biology


Caister Academic Press

Publisher Location

Norwich, Norfolk

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Central to bacterial pathogenicity is the precise and coordinated control of virulence gene expression in response to environmental cues encountered in the human host. This chapter focuses on the transcriptional regulation of Shigella virulence genes encoded by the large virulence plasmid, pINV, found in almost all Shigella species. We describe the silencing of pINV-encoded virulence genes by the chromosomally encoded nucleoid structuring protein H-NS, which serves as the backdrop for all other regulatory events on this plasmid. We then describe the four-tiered virulence regulatory cascade emphasizing the environmental stimuli, transcriptional regulators and mechanisms that govern virulence gene expression at each tier. Finally, we review other regulatory inputs that are received from the Shigella chromosome and their role in the modulation of virulence gene expression. We begin our discussion by describing the genetic organization of Shigella, its relatedness to Escherichia coli and the different forms of pINV carried by Shigella species to highlight how the regulatory cascades controlling Shigella virulence are, in large part, conserved across species. Overall, this chapter reveals that Shigella is a fascinating model for the study of virulence gene regulation, which promotes our understanding of Shigella pathogenesis and mechanisms of virulence gene regulation in other bacterial pathogens.