Tarragon essential oil as a source of bioactive compounds with anti-quorum sensing and anti-proteolytic activity against Pseudomonas spp. isolated from fish - in vitro, in silico and in situ approaches.

The present study aimed to evaluate the anti-quorum sensing (anti-QS) and anti-proteolytic potentials of tarragon essential oil (TEO) and its major compounds against food-associated Pseudomonas spp. The activities were verified by in vitro, in silico and in situ approaches. In this work, methyl eugenol (ME)- and β-phellandrene (β-PH)-rich TEO was investigated. TEO at subMIC increased the percentage of saturated fatty acids in the bacterial membranes (from 7 to 22%) and exhibited anti-quorum sensing via decreasing the efficiency of QS autoinducer synthesis [3-oxo-C12-HSL (from 2.028 μg/mL to <LOD), C4-HSL (from 1.312 μg/mL to <LOD) and PQS (from 0.007625 μg/mL to <LOD)]. ME and β-PH were docked into LasR, RhlR and PqsR proteins, with docking scores comparable to native autoinductors. The subMICs of TEO, ME and β-PH decreased the proteolysis in the examined bacteria by 33, 29, and 21% (in TSB medium) and by 29, 26, and 19% (in fish juice medium), respectively. Almost all genes encoding proteases were downregulated by the applied agents. The ME- and β-PH-rich TEO acts as an anti-QS agent and significantly suppresses the proteolytic activity of food-associated pseudomonads. It might therefore increase the quality of fish-based products, where Pseudomonas spp. predominate.