Unravelling the mysteries of virulence gene regulation in Salmonella typhimurium

Salmonella typhimurium, which causes gastroenteritis in calves and humans a s well as a typhoid-like disease in mice, uses numerous virulence factors t o infect its hosts. Genes encoding these factors are regulated by many envi ronmental conditions and regulatory pathways in vitro. Many virulence genes are specifically induced at particular sites during infection or in cultur ed host cells. The complex regulation of virulence genes observed in vitro may be necessary to restrict their expression to specific locations within the host. In vitro and in vivo studies provide clues about how virulence ge nes might be regulated in vivo. Future studies must assess the actual envir onmental signals and regulators that modulate each virulence gene in vivo a nd determine how multiple regulatory pathways are integrated to co-ordinate the appropriate expression of virulence factors at specific sites in vivo.