Abstract:This study aimed to explore theactivity and mechanism of carvacrol combined with ethyl-Nαlauroyl-L-arginate hydrochloride（LAE） against Pseudomonas fluorescens.Specifically，the activity was evaluated based on the minimum inhibitory concentration（MIC），checkerboard microdilution assay，and growth curve analysis.The antibacterial mechanism was explored through protein and nucleotide leakage，transmission electron microscopy，and electrophoresis of intracellular proteins.The quorum-sensing activity was evaluated with the indexes of biofilm formation，and swarming and swimming motility.The results showed that carvacrol and LAE displayed synergic activity against P.fluorescens，particularly the combination of carvacrol at 1/2 MIC and LAE at 1/16 MIC which achieved the inhibition rate of 97.9% at 24 h.The above combination could significantly enhance the permeability of cell membrane，thus leading to the rapid leakage of proteins and nucleic acids.As a result，the OD280and OD260values were 31.2 and 17.5 folds higher at 1 h，respectively.At 3 h，the intracellular electron density decreased and protein concentration declined by 84.1%，with bands of proteins becoming obviously shallow or even disappearing.The inhibition rates of biofilm formation，swarming motility，and swimming motility were 97.0%，92.5% and 65.0%，respectively.In conclusion，the combination of carvacrol and LAE can destroy P.fluorescens cells，leading to leakage of intracellula substances and thus exerting strong inhibitory effect on the bacteria.Moreover，the combination suppresses the quorum-sensing activity.