Ferulic acid and sinapic acid attenuate Pseudomonas aeruginosa biofilm formation and virulence by targeting the pqs quorum sensing system

Background: Quorum sensing (QS) is a bacterial intercellular communication mechanism mediated by extracellular signalling molecules that regulate gene expression. Pseudomonas quinolone signal (PQS) QS system, which is mediated by autoinducers of the quinolone family, is a fundamental QS component in Pseudomonas aeruginosa. It plays a crucial role in the formation and maintenance of biofilms and in the regulation of virulence factors. Phenolic acids, such as ferulic and sinapic acids, are plant secondary metabolites well known for their biological properties and have shown promise in modulating bacterial communication. The aim of this study was to evaluate the potential of ferulic and sinapic acids to inhibit the P. aeruginosa pqs QS system and underlying effects on biofilm structure and virulence factor production. Methods: The inhibitory effect on the pqs system was evaluated using bioreporter strains and bioluminescence-based assays. Biofilm architecture was analysed using optical coherence tomography, while virulence factors (pyoverdine, pyocyanin, total proteases, lipases, gelatinases and siderophores) production and motility was analysed by absorbance measurement and plate agar method. Results: Ferulic and sinapic acids inhibited pqs QS activity by 90 % at a concentration of 1000 μg mL-1. These compounds significantly changed biofilm architecture, reducing thickness from 96 μm-11 μm. They also markedly reduced the production of key virulence factors and impaired swarming motility. Conclusion: Ferulic and sinapic acids demonstrated strong inhibitory effects on the pqs QS system, leading to altered biofilm structure and reduced virulence. These findings support their potential as antipathogenic/antivirulence agents for prevention/treatment of P. aeruginosa biofilm-associated infections.