Identification of a conserved bacterial protein secretion system in Vibrio cholerae using the Dictyostelium host model system.
The bacterium Vibrio cholerae, like other human pathogens that reside in environmental reservoirs, survives predation by unicellular eukaryotes. Strains of the O1 and O139 serogroups cause cholera, whereas non-O1/non-O139 strains cause human infections through poorly defined mechanisms. Using Dictyostelium discoideum as a model host, we have identified a virulence mechanism in a non-O1/non-O139 V. cholerae strain that involves extracellular translocation of proteins that lack N-terminal hydrophobic leader sequences. Accordingly, we have named these genes "VAS" genes for virulence-associated secretion, and we propose that these genes encode a prototypic "type VI" secretion system. We show that vas genes are required for cytotoxicity of V. cholerae cells toward Dictyostelium amoebae and mammalian J774 macrophages by a contact-dependent mechanism. A large number of Gram-negative bacterial pathogens carry genes homologous to vas genes and potential effector proteins secreted by this pathway (i.e., hemolysin-coregulated protein and VgrG). Mutations in vas homologs in other bacterial species have been reported to attenuate virulence in animals and cultured macrophages. Thus, the genes encoding the VAS-related, type VI secretion system likely play an important conserved function in microbial pathogenesis and represent an additional class of targets for vaccine and antimicrobial drug-based therapies.
Pukatzki
Stefan
S
Department of Microbiology and Molecular Genetics, Harvard Medical School, 200 Longwood Avenue, Boston, MA 02115, USA.
Ma
Amy T
AT
Sturtevant
Derek
D
Krastins
Bryan
B
Sarracino
David
D
Nelson
William C
WC
Heidelberg
John F
JF
Mekalanos
John J
JJ
D000818:Animals; D001426:Bacterial Proteins / Q000737:chemistry; D002460:Cell Line; D022121:Cholera Vaccines; D004251:DNA Transposable Elements; D004023:Dictyostelium / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D015964:Gene Expression Regulation, Bacterial; D015723:Gene Library; D005798:Genes, Bacterial; D008264:Macrophages / Q000378:metabolism; D051379:Mice; D008954:Models, Biological; D008957:Models, Genetic; D021381:Protein Transport; D013997:Time Factors; D014734:Vibrio cholerae / Q000378:metabolism*; D014774:Virulence
D001426:Bacterial Proteins; D022121:Cholera Vaccines; D004251:DNA Transposable Elements