A SUBSTRATE OF THE CENTISOME-63 TYPE-III PROTEIN SECRETION SYSTEM OF SALMONELLA-TYPHIMURIUM IS ENCODED BY A CRYPTIC BACTERIOPHAGE

Salmonella enterica has evolved a type III protein secretion system th at allows these enteropathogens to translocate effector molecules dire ctly into the host cell cytoplasm, These effectors mediate a variety o f responses, including cytoskeletal rearrangements, cytokine productio n, and in certain cells, the induction of apoptosis, We report here th e characterization of a substrate of this secretion system in S. enter ica serovar typhimurium (Salmonella typhimurium) that is homologous to the SopE protein of Salmonella dublin implicated in bacterial entry i nto cultured epithelial cells, The sopE locus is located within a clus ter of genes that encode tail and tail fiber proteins of a cryptic P2- like prophage, outside of the centisome 63 pathogenicity island that e ncodes the invasion-associated type III secretion system, Southern hyb ridization analysis revealed that sopE is present in only a subset of S. enterica serovars and that the flanking bacteriophage genes are als o highly polymorphic Encoding effector proteins that are delivered thr ough type III secretion systems in highly mobile genetic elements mag allow pathogens to adapt rapidly by facilitating the assembly of an ap propriate set of effector proteins required for successful replication in a new environment.