Limits...
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.

Show MeSH
Indole production in V. anguillarum wild type (WT) and rpoS deletion mutant (ΔrpoS).(A) Indole production (bars) and cell density (lines) of V. anguillarum WT and ΔrpoS during growth in LB20 medium. (B) Relative expression of the indole biosynthesis gene tnaA in the wild type and the rpoS mutant. The expression was calculated relative to the RNA polymerase A subunit (rpoA) gene, expression in the wild type at the 6 h time point was set at 1 and the other data points were normalised accordingly. For both panels, error bars represent the standard error of three V. anguillarum cultures. ** indicates a significant difference when compared to the wild type at the respective time point (independent samples t-test; P<0.01).
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4216140&req=5

pone-0111801-g001: Indole production in V. anguillarum wild type (WT) and rpoS deletion mutant (ΔrpoS).(A) Indole production (bars) and cell density (lines) of V. anguillarum WT and ΔrpoS during growth in LB20 medium. (B) Relative expression of the indole biosynthesis gene tnaA in the wild type and the rpoS mutant. The expression was calculated relative to the RNA polymerase A subunit (rpoA) gene, expression in the wild type at the 6 h time point was set at 1 and the other data points were normalised accordingly. For both panels, error bars represent the standard error of three V. anguillarum cultures. ** indicates a significant difference when compared to the wild type at the respective time point (independent samples t-test; P<0.01).

Mentions: RpoS had previously been reported to increase indole production in E. coli by inducing the expression of the tryptophanase gene tnaA[18] and consequently, we investigated the impact of rpoS deletion on indole production in V. anguillarum. In contrast to what has been reported for E. coli, indole production was significantly increased in the rpoS mutant when compared to wild-type V. anguillarum (Figure 1A). The difference between the two strains in indole levels was two-fold in late exponential phase (12 h) and three-fold in stationary phase (24 h). In addition, we determined the relative expression levels of the indole biosynthesis gene tnaA in the wild type and rpoS deletion mutant by quantitative reverse transcriptase PCR, and found that the expression was significantly higher in the rpoS mutant at all sampling points, with between 3- and 12-fold difference between both strains (Figure 1B).


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)

Indole production in V. anguillarum wild type (WT) and rpoS deletion mutant (ΔrpoS).(A) Indole production (bars) and cell density (lines) of V. anguillarum WT and ΔrpoS during growth in LB20 medium. (B) Relative expression of the indole biosynthesis gene tnaA in the wild type and the rpoS mutant. The expression was calculated relative to the RNA polymerase A subunit (rpoA) gene, expression in the wild type at the 6 h time point was set at 1 and the other data points were normalised accordingly. For both panels, error bars represent the standard error of three V. anguillarum cultures. ** indicates a significant difference when compared to the wild type 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-g001: Indole production in V. anguillarum wild type (WT) and rpoS deletion mutant (ΔrpoS).(A) Indole production (bars) and cell density (lines) of V. anguillarum WT and ΔrpoS during growth in LB20 medium. (B) Relative expression of the indole biosynthesis gene tnaA in the wild type and the rpoS mutant. The expression was calculated relative to the RNA polymerase A subunit (rpoA) gene, expression in the wild type at the 6 h time point was set at 1 and the other data points were normalised accordingly. For both panels, error bars represent the standard error of three V. anguillarum cultures. ** indicates a significant difference when compared to the wild type at the respective time point (independent samples t-test; P<0.01).
Mentions: RpoS had previously been reported to increase indole production in E. coli by inducing the expression of the tryptophanase gene tnaA[18] and consequently, we investigated the impact of rpoS deletion on indole production in V. anguillarum. In contrast to what has been reported for E. coli, indole production was significantly increased in the rpoS mutant when compared to wild-type V. anguillarum (Figure 1A). The difference between the two strains in indole levels was two-fold in late exponential phase (12 h) and three-fold in stationary phase (24 h). In addition, we determined the relative expression levels of the indole biosynthesis gene tnaA in the wild type and rpoS deletion mutant by quantitative reverse transcriptase PCR, and found that the expression was significantly higher in the rpoS mutant at all sampling points, with between 3- and 12-fold difference between both strains (Figure 1B).

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