SalmonellaHost Cell Invasion Emerged by Acquisition of a Mosaic of Separate Genetic Elements, IncludingSalmonellaPathogenicity Island 1 (SPI1), SPI5, andsopE2

Salmonella spp. possess a conserved type III secretion system encoded within the pathogenicity island 1 (SPI1; centisome 63), which mediates translocation of effector proteins into the host cell cytosol to trigger responses such as bacterial internalization. Several translocated effector proteins are encoded in other regions of the Salmonella chromosome. It remains unclear how this complex chromosomal arrangement of genes for the type III...