Antibacterial Mechanism of Linalool against Pseudomonas fragi from Salmon

In this study, high-throughput sequencing was used to analyze the changes in the bacterial flora of salmon during cold storage, and a dominant spoilage bacterium in salmon stored at 4 ℃ was isolated, purified and identified as Pseudomonas fragi MS 02. Then, the antibacterial activity and mechanism of action of linalool against P. fragi MS 02 were investigated. The results showed that the bacteria flora composition of salmon stored at 4 ℃ changed with storage time. Photobacterium, Pseudomonas, Ralstonia and Acinetobacter were the dominant bacteria in salmon during storage. The relative abundance of Pseudomonas gradually increased with storage time, while P. fragi was the fastest growing strain during the storage period. It was found that linalool had a good antibacterial effect on P. fragi MS 02. Scanning electron microscopic (SEM) results showed that the bacterial cell membrane became wrinkled and sunken after treatment with linalool. By measuring electric conductivity, optical density at 260 nm (OD_{260 nm}), fluorescence intensity using fluorescein diacetate as a dye, and alkaline phosphatase (AKP) and Na⁺/K⁺-ATPase activities, it was confirmed that linalool could destroy the permeability and integrity of the cell membrane and cell wall of P. fragi, and affect energy metabolism, eventually resulting in cell death.