Pseudomonas aeruginosa (P. aeruginosa) biofilm formation is a crucial cause of enhanced antibiotic resistance. Quorum sensing (QS) is involved in regulating biofilm formation; QS inhibitors block the QS signaling pathway as a new strategy to address bacterial resistance. This study investigated the potential and mechanism of L-HSL (N-(3-cyclic butyrolactone)-4-trifluorophenylacetamide) as a QS inhibitor for P. aeruginosa. The results showed that L-HSL effectively inhibited the biofilm formation and dispersed the pre-formed biofilm of P. aeruginosa. The production of extracellular polysaccharides and the motility ability of P. aeruginosa were suppressed by L-HSL. C. elegans infection experiment showed that L-HSL was non-toxic and provided protection to C. elegans against P. aeruginosa infection. Transcriptomic analysis revealed that L-HSL downregulated genes related to QS pathways and biofilm formation. L-HSL exhibits a promising potential as a therapeutic drug for P. aeruginosa infection. Key points: • Chemical synthesis of N-(3-cyclic butyrolactone)-4-trifluorophenylacetamide, named L-HSL. • L-HSL does not generate survival pressure on the growth of P. aeruginosa and can inhibit the QS system. • KEGG enrichment analysis found that after L-HSL treatment, QS-related genes were downregulated.

Background: Pseudomonas aeruginosa (P. aeruginosa) is a type of pathogen that takes advantage of opportunities to infect and form biofilm during infection. Inhibiting biofilm formation is a promising approach for the treatment of biofilm-related infections. Methods: Here, Y0-C10-HSL (N-cyclopentyl-n-decanamide) was designed, synthesized, and tested for its effect on biofilm formation, motility, and the Caenorhabditis elegans (C. elegans) survival assay. In addition, the molecular mechanism of Y0-C10-HSL on P. aeruginosa biofilm formation was explored using transcriptome analysis. Results: At a concentration of 200 μmol/L Y0-C10-HSL, biofilm and exopolysaccharides were decreased by 38.5% and 29.3%, respectively; Y0-C10-HSL effectively dispersed the pre-formed biofilm and inhibited the motility ability of P. aeruginosa; and the C. elegans survival assay showed that Y0-C10-HSL was safe and provided protection to C. elegans against P. aeruginosa infection (the survival rates of C. elegans were higher than 74% and increased by 39%, 35.1%, and 47.5%, respectively, when treated with 200 μmol/L Y0-C10-HSL at 24, 48, and 80 h). Transcriptome analysis showed that 585 differentially expressed genes (DEGs) were found after treatment with 200 μmol/L Y0-C10-HSL, including 254 up-regulated DEGs and 331 down-regulated DEGs. The genes involved in the quorum sensing system and biofilm formation were down-regulated. Conclusions: Y0-C10-HSL inhibited the biofilm formation and dispersed the pre-formed biofilm of P. aeruginosa through down-regulated genes related to quorum sensing pathways and biofilm formation. These findings provide a theoretical foundation for the treatment and prevention of antibiotic resistance in clinical and environmental microorganisms such as P. aeruginosa.

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