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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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Related in: MedlinePlus

Impact of RpoS and indole signaling on the expression of genes involved in exopolysaccharide production in V. anguillarum.Relative expression of the exopolysaccharide biosynthesis gene wbfD (A) and the exopolysaccharide export gene wza (B) in wild type V. anguillarum and the rpoS deletion mutant (ΔrpoS). The expression was calculated relative to the RNA polymerase A subunit (rpoA) gene, expression in the wild type at the 6h time point was set at 1 and the other data points were normalised accordingly. Error bars represent the standard error of three different V. anguillarum cultures. ** denotes a significant difference when compared to the wild type strain without indole at the respective time point (independent samples t-test; P<0.01).
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pone-0111801-g003: Impact of RpoS and indole signaling on the expression of genes involved in exopolysaccharide production in V. anguillarum.Relative expression of the exopolysaccharide biosynthesis gene wbfD (A) and the exopolysaccharide export gene wza (B) in wild type V. anguillarum and the rpoS deletion mutant (ΔrpoS). The expression was calculated relative to the RNA polymerase A subunit (rpoA) gene, expression in the wild type at the 6h time point was set at 1 and the other data points were normalised accordingly. Error bars represent the standard error of three different V. anguillarum cultures. ** denotes a significant difference when compared to the wild type strain without indole at the respective time point (independent samples t-test; P<0.01).

Mentions: In order to confirm these observations, we determined the impact of RpoS and indole on the expression of the wbfD and wza genes by quantitative reverse transcriptase PCR, which are responsible for exopolysaccharide biosynthesis and export in V. anguillarum, respectively [7]. The expression of the exopolysaccharide synthesis gene wbfD was significantly lower in the rpoS deletion mutant than in the wild type at all sampling points (Figure 3A), whereas the expression of the exopolysaccharide export gene wza was higher in the rpoS mutant at all time points (Figure 3B). Furthermore, the addition of indole (both 50 and 100 µM) to the wild type resulted in an over 10-fold decrease in wbfD expression, whereas there was no effect on the expression of wza.


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 expression of genes involved in exopolysaccharide production in V. anguillarum.Relative expression of the exopolysaccharide biosynthesis gene wbfD (A) and the exopolysaccharide export gene wza (B) in wild type V. anguillarum and the rpoS deletion mutant (ΔrpoS). The expression was calculated relative to the RNA polymerase A subunit (rpoA) gene, expression in the wild type at the 6h time point was set at 1 and the other data points were normalised accordingly. Error bars represent the standard error of three different V. anguillarum cultures. ** denotes a significant difference when compared to the wild type strain without indole at the respective time point (independent samples t-test; P<0.01).
© Copyright Policy
Related In: Results  -  Collection

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

pone-0111801-g003: Impact of RpoS and indole signaling on the expression of genes involved in exopolysaccharide production in V. anguillarum.Relative expression of the exopolysaccharide biosynthesis gene wbfD (A) and the exopolysaccharide export gene wza (B) in wild type V. anguillarum and the rpoS deletion mutant (ΔrpoS). The expression was calculated relative to the RNA polymerase A subunit (rpoA) gene, expression in the wild type at the 6h time point was set at 1 and the other data points were normalised accordingly. Error bars represent the standard error of three different V. anguillarum cultures. ** denotes a significant difference when compared to the wild type strain without indole at the respective time point (independent samples t-test; P<0.01).
Mentions: In order to confirm these observations, we determined the impact of RpoS and indole on the expression of the wbfD and wza genes by quantitative reverse transcriptase PCR, which are responsible for exopolysaccharide biosynthesis and export in V. anguillarum, respectively [7]. The expression of the exopolysaccharide synthesis gene wbfD was significantly lower in the rpoS deletion mutant than in the wild type at all sampling points (Figure 3A), whereas the expression of the exopolysaccharide export gene wza was higher in the rpoS mutant at all time points (Figure 3B). Furthermore, the addition of indole (both 50 and 100 µM) to the wild type resulted in an over 10-fold decrease in wbfD expression, whereas there was no effect on the expression of wza.

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
Related in: MedlinePlus