Abstract
The demand for reduced chemical preservative usage is currently growing, and natural preservatives are being developed to protect seafood. With its excellent antibacterial properties, linalool has been utilized widely in industries. However, its antibacterial mechanisms remain poorly studied. Here, untargeted metabolomics was applied to explore the mechanism of Shewanella putrefaciens cells treated with linalool. Results showed that linalool exhibited remarkable antibacterial activity against S. putrefaciens, with 1.5 µL/mL minimum inhibitory concentration (MIC). The growth of S. putrefaciens was suppressed completely at 1/2 MIC and 1 MIC levels. Linalool treatment reduced the membrane potential (MP); caused the leakage of alkaline phosphatase (AKP); and released the DNA, RNA, and proteins of S. putrefaciens, thus destroying the cell structure and expelling the cytoplasmic content. A total of 170 differential metabolites (DMs) were screened using metabolomics analysis, among which 81 species were upregulated and 89 species were downregulated after linalool treatment. These DMs are closely related to the tricarboxylic acid (TCA) cycle, glycolysis, amino acid metabolism, pantothenate and CoA biosynthesis, aminoacyl-tRNA biosynthesis, and glycerophospholipid metabolism. In addition, linalool substantially affected the activity of key enzymes, such as succinate dehydrogenase (SDH), pyruvate kinase (PK), ATPase, and respiratory chain dehydrogenase. The results provided some insights into the antibacterial mechanism of linalool against S. putrefaciens and are important for the development and application of linalool in seafood preservation.
Highlights
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.Linalool (C10H18O), known as 3,7-dimethyl-1,6-octadien-3-ol, is widely found in the essential oils (EOs) extracted from more than 200 plants worldwide, such as green huajiao EOs (28.2% linalool), Forsythia koreana leaf EOs (10.68% linalool), and pine needle EOs (24.47% linalool) [1,2,3]
The alkaline phosphatase (AKP) concentration in the suspension of all tested strains treated with linalool (1/2 minimum inhibitory concentration (MIC) and MIC) increased remarkably within 2 h
Compared with 1/2 MIC linalool, the 1 MIC group was more effective in increasing the concentration of AKP in the cell suspension, suggesting that high linalool concentrations (MIC) can destroy bacterial cell walls and enhance the membrane leakage of AKP
Summary
Linalool (C10H18O), known as 3,7-dimethyl-1,6-octadien-3-ol, is widely found in the essential oils (EOs) extracted from more than 200 plants worldwide, such as green huajiao EOs (28.2% linalool), Forsythia koreana leaf EOs (10.68% linalool), and pine needle EOs (24.47% linalool) [1,2,3]. Shewanella putrefaciens, the Gram-negative motile bacteria belonging to the family Shewanellaceae, is a seafood spoilage organism (SSO) for cryopreserved fresh fish, that is S. putrefaciens is still a great threat to seafood even under cold storage condition [5]. This opportunistic bacteria is associated with various clinically important infections and diseases, especially in the tropics and during summer months in temperate zones [6]. The combination of cinnamaldehyde and Ferulago angulata essential oil can inhibit the growth of S. putrefaciens and prolong the shelf life of olive flounder fillets [8]
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