Salmonella interactions with host cells: Type III secretion at work

The bacterial pathogen Salmonella enterica has evolved a very sophisticated functional interface with its vertebrate hosts. At the center of this inte rface is a specialized organelle, the type III secretion system, that direc ts the translocation of bacterial proteins into the host cell. Salmonella s pp. encode two such systems that deliver a remark-able array of bacterial p roteins capable of modulating a variety of cellular functions, including ac tin cytoskeleton dynamics, nuclear responses, and endocytic trafficking. Ma ny of these bacterial proteins operate by faithful mimicry of host proteins , in some cases representing the result of extensive molecular tinkering an d convergent evolution. The coordinated action of these type III secreted p roteins secures the replication and survival of the bacteria avoiding overt damage to the host. The study of this remarkable pathogen is not only illu minating general paradigms in microbial pathogenesis but is also providing valuable insight into host cell functions.