title: RpoS and indole signaling control the virulence of Vibrio anguillarum towards gnotobiotic sea bass (Dicentrarchus labrax) larvae.
abstract: Quorum sensing, bacterial cell-to-cell communication with small signal molecules, controls the virulence of many pathogens. In contrast to other vibrios, neither the VanI/VanR acylhomoserine lactone quorum sensing system, nor the three-channel quorum sensing system affects virulence of the economically important aquatic pathogen Vibrio anguillarum. Indole is another molecule that recently gained attention as a putative signal molecule. The data presented in this study indicate that indole signaling and the alternative sigma factor RpoS have a significant impact on the virulence of V. anguillarum. Deletion of rpoS resulted in increased expression of the indole biosynthesis gene tnaA and in increased production of indole. Both rpoS deletion and the addition of exogenous indole (50-100 µM) resulted in decreased biofilm formation, exopolysaccharide production (a phenotype that is required for pathogenicity) and expression of the exopolysaccharide synthesis gene wbfD. Further, indole inhibitors increased the virulence of the rpoS deletion mutant, suggesting that indole acts downstream of RpoS. Finally, in addition to the phenotypes found to be affected by indole, the rpoS deletion mutant also showed increased motility and decreased sensitivity to oxidative stress.
authors.affiliation: Laboratory of Aquaculture and Artemia Reference Center, Ghent University, Ghent, Belgium.
authors.forename: Xuan
authors.initials: X
authors.lastname: Li
authors.affiliation: Laboratory of Aquaculture and Artemia Reference Center, Ghent University, Ghent, Belgium.
authors.forename: Qian
authors.initials: Q
authors.lastname: Yang
authors.affiliation: Laboratory of Aquaculture and Artemia Reference Center, Ghent University, Ghent, Belgium.
authors.forename: Kristof
authors.initials: K
authors.lastname: Dierckens
authors.affiliation: Southern Research Institute, Birmingham, Alabama, United States of America; Department of Molecular Biology, Umeå University, Umeå, Sweden.
authors.forename: Debra L
authors.initials: DL
authors.lastname: Milton
authors.affiliation: Laboratory of Aquaculture and Artemia Reference Center, Ghent University, Ghent, Belgium; Laboratory of Microbial Ecology and Technology, Ghent University, Ghent, Belgium.
authors.forename: Tom
authors.initials: T
authors.lastname: Defoirdt
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000378:metabolism*; D001492:Bass / Q000382:microbiology*; D018441:Biofilms / Q000254:growth & development; D001704:Biopolymers / Q000378:metabolism; D017353:Gene Deletion; D005798:Genes, Bacterial; D005856:Germ-Free Life; D007211:Indoles / Q000378:metabolism*; D007814:Larva; D018384:Oxidative Stress; D010641:Phenotype; D012808:Sigma Factor / Q000378:metabolism*; D015398:Signal Transduction; D014733:Vibrio / Q000235:genetics / Q000472:pathogenicity* / Q000502:physiology; D014774:Virulence
chemical_list: D001426:Bacterial Proteins; D001704:Biopolymers; D007211:Indoles; D012808:Sigma Factor; C069567:sigma factor KatF protein, Bacteria; C030374:indole