Linoleic acid inhibits Pseudomonas aeruginosa biofilm formation by activating diffusible signal factor-mediated quorum sensing

Bacterial biofilm formation causes serious problems in various fields of medical, clinical, and industrial settings. Antibiotics and biocide treatments are typical methods used to remove bacterial biofilms, but biofilms are difficult to remove effectively from surfaces due to their increased resistance. An alternative approach to treatment with antimicrobial agents is using biofilm inhibitors that regulate biofilm development without inhibiting bacterial growth. In the present study, we found that linoleic acid (LA), a plant unsaturated fatty acid, inhibits biofilm formation under static and continuous conditions without inhibiting the growth of Pseudomonas aeruginosa. LA also influenced the bacterial motility, extracellular polymeric substance production, and biofilm dispersion by decreasing the intracellular cyclic diguanylate concentration through increased phosphodiesterase activity. Furthermore, quantitative gene expression analysis demonstrated that LA induced the expression of genes associated with diffusible signaling factor-mediated quorum sensing that can inhibit or induce the dispersion of P. aeruginosa biofilms. These results suggest that LA is functionally and structurally similar to a P. aeruginosa diffusible signaling factor (cis-2-decenoic acid) and, in turn, act as an agonist molecule in biofilm dispersion.