title: SseL is a salmonella-specific translocated effector integrated into the SsrB-controlled salmonella pathogenicity island 2 type III secretion system.
abstract: Bacterial pathogens use horizontal gene transfer to acquire virulence factors that influence host colonization, alter virulence traits, and ultimately shape the outcome of disease following infection. One hallmark of the host-pathogen interaction is the prokaryotic type III secretion system that translocates virulence factors into host cells during infection. Salmonella enterica possesses two type III secretion systems that are utilized during host colonization and intracellular replication. Salmonella pathogenicity island 2 (SPI2) is a genomic island containing approximately 30 contiguous genes required to assemble a functional secretion system including the two-component regulatory system called SsrA-SsrB that positively regulates transcription of the secretion apparatus. We used transcriptional profiling with DNA microarrays to search for genes that coregulate with the SPI2 type III secretion machinery in an SsrB-dependent manner. Here we report the identification of a Salmonella-specific translocated effector called SseL that is required for full virulence during murine typhoid-like disease. Analysis of infected macrophages using fluorescence-activated cell sorting revealed that sseL is induced inside cells and requires SsrB for expression. SseL is retained predominantly in the cytoplasm of infected cells following translocation by the type III system encoded in SPI2. Animal infection experiments with sseL mutant bacteria indicate that integration of SseL into the SsrB response regulatory system contributes to systemic virulence of this pathogen.
authors.affiliation: Department of Biochemistry and Biomedical Sciences, McMaster University, Health Sciences Centre, Room 4H17, 1200 Main St. West, Hamilton, Ontario L8N 3Z5, Canada. coombes@mcmaster.ca
authors.forename: Brian K
authors.initials: BK
authors.lastname: Coombes
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Lowden
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Bishop
authors.forename: Mark E
authors.initials: ME
authors.lastname: Wickham
authors.forename: Nat F
authors.initials: NF
authors.lastname: Brown
authors.forename: Nancy
authors.initials: N
authors.lastname: Duong
authors.forename: Suzanne
authors.initials: S
authors.lastname: Osborne
authors.forename: Ohad
authors.initials: O
authors.lastname: Gal-Mor
authors.forename: B Brett
authors.initials: BB
authors.lastname: Finlay
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D002460:Cell Line; D003593:Cytoplasm / Q000737:chemistry; D004195:Disease Models, Animal; D004847:Epithelial Cells / Q000382:microbiology; D005434:Flow Cytometry; D017353:Gene Deletion; D015964:Gene Expression Regulation, Bacterial; D044404:Genomic Islands / Q000235:genetics*; D006801:Humans; D008264:Macrophages / Q000382:microbiology; D051379:Mice; D008810:Mice, Inbred C57BL; D016254:Mutagenesis, Insertional; D020411:Oligonucleotide Array Sequence Analysis; D021381:Protein Transport / Q000235:genetics; D012481:Salmonella Infections, Animal / Q000382:microbiology*; D012486:Salmonella typhimurium / Q000235:genetics / Q000472:pathogenicity* / Q000502:physiology*; D014157:Transcription Factors / Q000235:genetics / Q000502:physiology; D037521:Virulence Factors / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism / Q000502:physiology*
chemical_list: D001426:Bacterial Proteins; C119761:SsrB protein, Salmonella typhimurium; D014157:Transcription Factors; D037521:Virulence Factors