Effect of black pepper essential oil on quorum sensing and efflux pump systems in the fish-borne spoiler Pseudomonas psychrophila KM02 identified by RNA-seq, RT-qPCR and molecular docking analyses

Given the increasing consumption of aquatic foods and green consumerism, efficient methods for extending the shelf-life and maintaining the safety of seafood are urgently required. The present study aimed to evaluate the effect of black pepper essential oil (BPEO) and its major compounds – limonene (LIM) and beta-caryophyllene (CAR) on quorum sensing (QS) and efflux pump (EP) systems in Pseudomonas psychrophila KM02. Transcriptomic analysis was performed to select antimicrobial resistance genes that were only truly expressed within the system mimicking the food matrices. Compounds analyzed at subinhibitory concentrations (subMICs) (135, 65 and 35 μL/mL) reduced QS autoinducer synthesis to levels lower than the limit of detection and decreased proteolytic activity and exopolysaccharide synthesis by 35, 29 and 28%, and by 58, 32 and 41%, respectively. These phenotypic results were confirmed by changes in the ratio of expression of selected genes. Furthermore, the anti-QS activity and anti-EP of LIM and CAR were evaluated by molecular docking analyses with QS receptor proteins (LasR, RhlR, TraR, and PqsR) and inner membrane EP proteins (MuxB, MexB, and Mfs). The mRNA transcript levels of membrane fusion and outer membrane proteins, and transcription of repressor regulators MarR and TetR were considerable decreased. Our work showed that BPEO major compounds affected the functioning of the QS and EP system in KM02 and consequently reduced the spoilage potential.