Regulation of virulence gene expression in Shigella flexneri, a facultative intracellular pathogen

Shigella flexneri and its close relatives are facultative intracellular pat hogens of humans and are the etiological agents of bacillary dysentery. The se bacteria secrete proteins that enable them to enter human epithelial cel ls via an elaborate and fascinating cell biology. This behaviour depends on a complicated regulon of virulence genes, whose expression is controlled i n response to a multiplicity of environmental signals. This review describe s and attempts to interpret these gene control mechanisms.