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RpoS and indole signaling control the virulence of Vibrio anguillarum towards gnotobiotic sea bass (Dicentrarchus labrax) larvae.

Li X, Yang Q, Dierckens K, Milton DL, Defoirdt T - PLoS ONE (2014)

Bottom Line: 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.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.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Aquaculture and Artemia Reference Center, Ghent University, Ghent, Belgium.

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.

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Impact of RpoS and indole signaling on the virulence of V. anguillarum towards gnotobiotic sea bass larvae.Survival of gnotobiotic sea bass larvae challenged with V. anguillarum wild type (WT), with or without indole (either added to the sea bass rearing water or added to V. anguillarum cultures and removed prior to inoculation into the rearing water), and the rpoS deletion mutant (ΔrpoS), with or without the indole inhibitors isatin and acetyl-tryptophan (both added to the rearing water at 50 µM) 8 days after inoculation of the pathogen into the rearing water. Error bars represent the standard error of 10 fish cultures. Different letters denote significant differences (ANOVA with Tukey's post-hoc test; P<0.01). “Control” refers to unchallenged larvae that were otherwise treated in the same way as in all other treatments.
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pone-0111801-g002: Impact of RpoS and indole signaling on the virulence of V. anguillarum towards gnotobiotic sea bass larvae.Survival of gnotobiotic sea bass larvae challenged with V. anguillarum wild type (WT), with or without indole (either added to the sea bass rearing water or added to V. anguillarum cultures and removed prior to inoculation into the rearing water), and the rpoS deletion mutant (ΔrpoS), with or without the indole inhibitors isatin and acetyl-tryptophan (both added to the rearing water at 50 µM) 8 days after inoculation of the pathogen into the rearing water. Error bars represent the standard error of 10 fish cultures. Different letters denote significant differences (ANOVA with Tukey's post-hoc test; P<0.01). “Control” refers to unchallenged larvae that were otherwise treated in the same way as in all other treatments.

Mentions: The rpoS deletion mutant showed a significantly decreased virulence towards sea bass larvae, with no significant difference in survival when compared to unchallenged larvae (Figure 2). This indicates that RpoS plays an important role in the pathogenicity of V. anguillarum.


RpoS and indole signaling control the virulence of Vibrio anguillarum towards gnotobiotic sea bass (Dicentrarchus labrax) larvae.

Li X, Yang Q, Dierckens K, Milton DL, Defoirdt T - PLoS ONE (2014)

Impact of RpoS and indole signaling on the virulence of V. anguillarum towards gnotobiotic sea bass larvae.Survival of gnotobiotic sea bass larvae challenged with V. anguillarum wild type (WT), with or without indole (either added to the sea bass rearing water or added to V. anguillarum cultures and removed prior to inoculation into the rearing water), and the rpoS deletion mutant (ΔrpoS), with or without the indole inhibitors isatin and acetyl-tryptophan (both added to the rearing water at 50 µM) 8 days after inoculation of the pathogen into the rearing water. Error bars represent the standard error of 10 fish cultures. Different letters denote significant differences (ANOVA with Tukey's post-hoc test; P<0.01). “Control” refers to unchallenged larvae that were otherwise treated in the same way as in all other treatments.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4216140&req=5

pone-0111801-g002: Impact of RpoS and indole signaling on the virulence of V. anguillarum towards gnotobiotic sea bass larvae.Survival of gnotobiotic sea bass larvae challenged with V. anguillarum wild type (WT), with or without indole (either added to the sea bass rearing water or added to V. anguillarum cultures and removed prior to inoculation into the rearing water), and the rpoS deletion mutant (ΔrpoS), with or without the indole inhibitors isatin and acetyl-tryptophan (both added to the rearing water at 50 µM) 8 days after inoculation of the pathogen into the rearing water. Error bars represent the standard error of 10 fish cultures. Different letters denote significant differences (ANOVA with Tukey's post-hoc test; P<0.01). “Control” refers to unchallenged larvae that were otherwise treated in the same way as in all other treatments.
Mentions: The rpoS deletion mutant showed a significantly decreased virulence towards sea bass larvae, with no significant difference in survival when compared to unchallenged larvae (Figure 2). This indicates that RpoS plays an important role in the pathogenicity of V. anguillarum.

Bottom Line: 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.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.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Aquaculture and Artemia Reference Center, Ghent University, Ghent, Belgium.

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.

Show MeSH