A Shigella flexneri virulence plasmid encoded factor controls production of outer membrane vesicles.
Shigella spp. use a repertoire of virulence plasmid-encoded factors to cause shigellosis. These include components of a Type III Secretion Apparatus (T3SA) that is required for invasion of epithelial cells and many genes of unknown function. We constructed an array of 99 deletion mutants comprising all genes encoded by the virulence plasmid (excluding those known to be required for plasmid maintenance) of Shigella flexneri. We screened these mutants for their ability to bind the dye Congo red: an indicator of T3SA function. This screen focused our attention on an operon encoding genes that modify the cell envelope including virK, a gene of partially characterized function. We discovered that virK is required for controlled release of proteins to the culture supernatant. Mutations in virK result in a temperature-dependent overproduction of outer membrane vesicles (OMVs). The periplasmic chaperone/protease DegP, a known regulator of OMV production in Escherichia coli (encoded by a chromosomal gene), was found to similarly control OMV production in S. flexneri. Both virK and degP show genetic interactions with mxiD, a structural component of the T3SA. Our results are consistent with a model in which VirK and DegP relieve the periplasmic stress that accompanies assembly of the T3SA.
Department of Microbiology and Immunology, Dalhousie University Halifax, NS, Canada B3H 4R2.
Saima
S
Sidik
Department of Microbiology and Immunology, Dalhousie University Halifax, NS, Canada B3H 4R2.
Haila
H
Kottwitz
Department of Microbiology and Immunology, Dalhousie University Halifax, NS, Canada B3H 4R2.
Jeremy
J
Benjamin
Department of Microbiology and Immunology, Dalhousie University Halifax, NS, Canada B3H 4R2.
Julie
J
Ryu
Department of Microbiology and Immunology, Dalhousie University Halifax, NS, Canada B3H 4R2.
Ameer
A
Jarrar
Canadian Food Inspection Agency, Dartmouth Laboratory, Dartmouth, NS Canada B3B 1Y9.
Rafael
R
Garduno
Department of Microbiology and Immunology, Dalhousie University Halifax, NS, Canada B3H 4R2 john.rohde@dal.ca.
John R
JR
Rohde
D001425:Bacterial Outer Membrane Proteins / Q000235:genetics; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D003224:Congo Red / Q000737:chemistry / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D005798:Genes, Bacterial / Q000235:genetics; D006367:HeLa Cells; D006801:Humans; D009154:Mutation; D033903:Periplasmic Proteins / Q000235:genetics; D010957:Plasmids / Q000235:genetics* / Q000378:metabolism*; D022142:Secretory Vesicles / Q000378:metabolism*; D012763:Shigella flexneri / Q000235:genetics* / Q000472:pathogenicity*; D013696:Temperature; D014774:Virulence / Q000235:genetics*
D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; C079723:MxiD protein, Shigella; D033903:Periplasmic Proteins; D003224:Congo Red
Shigella; outer membrane vesicles; virulence