Benzyl isothiocyanate suppresses biofilms and virulence factors as a quorum sensing inhibitor in Pseudomonas fluorescens

Pseudomonas fluorescens, a specific spoilage organism, can control cell density and various physiological processes through quorum sensing (QS). Quorum sensing inhibitors (QSIs) are a crucial strategy for enhancing food quality and safety. In this study, benzyl isothiocyanate (BITC) at subminimum inhibitory concentrations (MICs) promoted protein and nucleic acid leakage, β-galactosidase activity and the relative fluorescence intensity of the membrane potential in P. fluorescens. N-butyryl-l-homoserine lactone (C4-HSL) and N-decanoyl-l-homoserine lactone (C10-HSL) were detected in P. fluorescens by ultra-performance liquid chromatography-mass spectrometry (UPLC-MS/MS). C4-HSL and C10-HSL are known to orchestrate the QS of gram-negative bacteria. The inhibition rates of C4-HSL and C10-HSL by BITC at 1/2 MIC were 54.0%–96.2% and 31.6%–70.5%, respectively, after cultured with P. fluorescens for 6–24 h. The inhibitory effects of BITC at 1/4 MIC on P. fluorescens biofilm formation, extracellular polysaccharide production, and motility were enhanced in the presence of exogenous C4-HSL. Moreover, sub-MICs of BITC markedly downregulated the relative expression of QS-related genes, and the molecular docking results also showed excellent binding ability of BITC to QS proteins. This study demonstrated the feasibility of BITC as a QSI, whereby exogenous C4-HSL promoted the ability of BITC to disturb the QS system in P. fluorescens.