Salmonella enterica serovar typhimurium pathogenicity island 1-encoded type III secretion system translocases mediate intimate attachment to nonphagocytic cells.
Delivery of bacterial proteins into mammalian cells by type III secretion systems (TTSS) is thought to require the intimate association of bacteria with target cells. The molecular bases of this intimate association appear to be different in different bacteria involving TTSS components, as well as surface determinants not associated with TTSS. We show here that the protein translocases SipB, SipC, and SipD of the Salmonella enterica serovar Typhimurium pathogenicity island 1 (SPI-1)-encoded TTSS are required for the intimate association of these bacteria with mammalian cells. S. Typhimurium mutant strains lacking any of the translocases were defective for intimate attachment. Immunofluorescence microscopy showed that SipD is present on the bacterial surface prior to bacterial contact with host cells. In contrast, SipB and SipC were detected on the bacterial surface only subsequent to bacterial contact with the target cell. We conclude that the coordinated deployment and interaction between the protein translocases mediate the SPI-1 TTSS-dependent intimate association of S. Typhimurium with host cells.
Lara-Tejero
María
M
Section of Microbial Pathogenesis, Yale University School of Medicine, Boyer Center for Molecular Medicine, New Haven, CT 06536, USA.
Galán
Jorge E
JE
D000942:Antigens, Bacterial / Q000235:genetics / Q000502:physiology*; D001422:Bacterial Adhesion; D001426:Bacterial Proteins / Q000235:genetics / Q000502:physiology*; D002460:Cell Line; D004847:Epithelial Cells / Q000382:microbiology; D017353:Gene Deletion; D044404:Genomic Islands; D006801:Humans; D008565:Membrane Proteins / Q000235:genetics / Q000502:physiology*; D012486:Salmonella typhimurium / Q000235:genetics / Q000472:pathogenicity* / Q000502:physiology
D000942:Antigens, Bacterial; D001426:Bacterial Proteins; D008565:Membrane Proteins; C094578:Salmonella invasion protein C; C107188:SspD protein, Salmonella typhimurium; C094579:invasion protein B, Salmonella typhimurium