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In this study, linalool, one of the principal components of essential oils, was used as an antibacterial agent to investigate the antibacterial activity and mechanism of linalool against Pseudomonas fluorescens. The reduction in membrane potential (MP), leakage of alkaline phosphatase (AKP) and the release of macromolecules, including DNA, RNA and protein confirmed that damage to cell wall membrane structure and leakage of cytoplasmic contents were due to the linalool treatment. Furthermore, the decrease of enzyme activity, including the succinate dehydrogenase (SDH), malate dehydrogenase (MDH), pyruvate kinase (PK), and ATPase indicated that linalool could lead to metabolic dysfunction and inhibit energy synthesis. In addition, the activity of respiratory chain dehydrogenase and metabolic activity of respiration indicated that linalool inhibits cellular respiration. These results revealed that linalool had strong antibacterial activity against P. fluorescens via membrane damage, bacterial metabolic and oxidative respiratory perturbations, interfering in cellular functions and even causing cell death. It was suggested that linalool may be a new potential source as food antiseptics in food systems.

3-Carene is an antimicrobial monoterpene that occurs naturally in a variety of plants and has an ambiguous antibacterial mechanism against food-borne germs. The antibacterial effects and action mechanism of 3-carene against Gram-positive Brochothrix thermosphacta ACCC 03870 and Gram-negative Pseudomonas fluorescens ATCC 13525 were studied. Scanning electron microscopy (SEM) examination and leakage of alkaline phosphatase (AKP) verified that 3-carene caused more obvious damage to the morphology and wall structure of B. thermosphacta than P. fluorescens. The release of potassium ions and proteins, the reduction in membrane potential (MP), and fluorescein diacetate (FDA) staining further confirmed that the loss of the barrier function of the cell membrane and the leakage of cytoplasmic contents were due to the 3-carene treatment. Furthermore, the disorder of succinate dehydrogenase (SDH), malate dehydrogenase (MDH), pyruvate kinase (PK), and ATP content indicated that 3-carene could lead to metabolic dysfunction and inhibit energy synthesis. In addition, the results from the fluorescence analysis revealed that 3-carene could probably bind to bacterial DNA and affect the conformation and structure of genomic DNA. These results revealed that 3-carene had strong antibacterial activity against B. thermosphacta and P. fluorescens via membrane damage, bacterial metabolic perturbations, and genomic DNA structure disruption, interfering in cellular functions and even causing cell death.