Bicyclic compounds repress membrane vesicle production and Pseudomonas quinolone signal synthesis in Pseudomonas aeruginosa.

Pseudomonas aeruginosa secretes membrane vesicles (MVs) that deliver several virulence factors as a cargo. We found that indole and its derivative compounds, including 4-hydroxyindole, 5-hydroxyindole, 6-hydroxyindole and isatin, repress MV production significantly. These compounds also repressed the synthesis of Pseudomonas quinolone signal (PQS), which is one of the quorum-sensing signals that upregulate virulence gene expression and positively control MV production. Moreover, we showed that other bicyclic compounds, including 1-naphthol, 2-naphthol, 2,3-dihydroxynaphthalene, 1-aminonaphthalene and 8-quinolinol, significantly repress MV production and PQS synthesis. In conclusion, we provide new information about the chemical structures that inhibit P. aeruginosa virulence.