title: N-acylhomoserine lactones involved in quorum sensing control the type VI secretion system, biofilm formation, protease production, and in vivo virulence in a clinical isolate of Aeromonas hydrophila.
abstract: In this study, we delineated the role of N-acylhomoserine lactone(s) (AHLs)-mediated quorum sensing (QS) in the virulence of diarrhoeal isolate SSU of Aeromonas hydrophila by generating a double knockout Delta ahyRI mutant. Protease production was substantially reduced in the Delta ahyRI mutant when compared with that in the wild-type (WT) strain. Importantly, based on Western blot analysis, the Delta ahyRI mutant was unable to secrete type VI secretion system (T6SS)-associated effectors, namely haemolysin coregulated protein and the valine-glycine repeat family of proteins, while significant levels of these effectors were detected in the culture supernatant of the WT A. hydrophila. In contrast, the production and translocation of the type III secretion system (T3SS) effector AexU in human colonic epithelial cells were not affected when the ahyRI genes were deleted. Solid surface-associated biofilm formation was significantly reduced in the Delta ahyRI mutant when compared with that in the WT strain, as determined by a crystal violet staining assay. Scanning electron microscopic observations revealed that the Delta ahyRI mutant was also defective in the formation of structured biofilm, as it was less filamentous and produced a distinct exopolysaccharide on its surface when compared with the structured biofilm produced by the WT strain. These effects of AhyRI could be complemented either by expressing the ahyRI genes in trans or by the exogeneous addition of AHLs to the Delta ahyRI/ahyR(+) complemented strain. In a mouse lethality experiment, 50 % attenuation was observed when we deleted the ahyRI genes from the parental strain of A. hydrophila. Together, our data suggest that AHL-mediated QS modulates the virulence of A. hydrophila SSU by regulating the T6SS, metalloprotease production and biofilm formation.
authors.affiliation: Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, TX 77555-1070, USA.
authors.forename: Bijay K
authors.initials: BK
authors.lastname: Khajanchi
authors.affiliation: Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, TX 77555-1070, USA.
authors.forename: Jian
authors.initials: J
authors.lastname: Sha
authors.affiliation: Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, TX 77555-1070, USA.
authors.forename: Elena V
authors.initials: EV
authors.lastname: Kozlova
authors.affiliation: Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, TX 77555-1070, USA.
authors.forename: Tatiana E
authors.initials: TE
authors.lastname: Erova
authors.affiliation: Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, TX 77555-1070, USA.
authors.forename: Giovanni
authors.initials: G
authors.lastname: Suarez
authors.affiliation: Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, TX 77555-1070, USA.
authors.forename: Johanna C
authors.initials: JC
authors.lastname: Sierra
authors.affiliation: Department of Pathology, University of Texas Medical Branch, Galveston, TX 77555-1070, USA.
authors.forename: Vsevolod L
authors.initials: VL
authors.lastname: Popov
authors.affiliation: Department of Medical and Research Technology, University of Maryland School of Medicine, Baltimore, MD 21201, USA.
authors.forename: Amy J
authors.initials: AJ
authors.lastname: Horneman
authors.affiliation: Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, TX 77555-1070, USA.
authors.forename: Ashok K
authors.initials: AK
authors.lastname: Chopra
mesh_terms: D054742:Acyl-Butyrolactones / Q000378:metabolism*; D016980:Aeromonas hydrophila / Q000235:genetics / Q000378:metabolism* / Q000472:pathogenicity; D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D018441:Biofilms; D002460:Cell Line; D015964:Gene Expression Regulation, Bacterial; D055786:Gene Knockout Techniques; D005816:Genetic Complementation Test; D006801:Humans; D051379:Mice; D010447:Peptide Hydrolases / Q000378:metabolism; D053038:Quorum Sensing; D018085:Regulon; D014774:Virulence
chemical_list: D054742:Acyl-Butyrolactones; C108088:AhyRI protein, Aeromonas; D001426:Bacterial Proteins; D010447:Peptide Hydrolases