桉叶精油对水产品中4种微生物的抑菌效果及抑菌机理

本文研究了桉叶精油对水产品中4种微生物的体外抑菌活性及其抑菌机理。通过滤纸片法和倍比稀释法分别测定抑菌圈直径(DIZ)和最低抑菌浓度(MIC),分析植物精油(桉叶精油、薄荷精油、茶树精油、丁香精油)对水产品中4种常见微生物(大肠杆菌、金黄色葡萄球菌、腐败希瓦氏菌和副溶血性弧菌)的抑菌效果;进一步以腐败希瓦氏菌和金黄色葡萄球菌为研究对象,通过扫描电镜、透射电镜、电导率、核酸含量、细胞内ATP含量分析植物精油的抑菌机理。结果表明,桉叶精油对大肠杆菌、腐败希瓦氏菌、副溶血性弧菌和金黄色葡萄球菌的抑菌圈直径分别为33.33、27.87、38.88、39.61 mm,对大肠杆菌、腐败希瓦氏菌、副溶血性弧菌和金黄色葡萄球菌的MIC值分别为1.00、1.25、0.75、0.63 μL/mL,在4种植物精油中显示出最强的抗菌活性。桉叶精油改变了腐败希瓦氏菌和金黄色葡萄球菌的细胞形态和超微结构,加了细胞膜的通透性,破坏了细胞膜的完整性,造成细胞内容物的泄露及细胞生理功能紊乱,从而导致细菌的死亡。本实验将为桉叶精油作为一种天然抑菌物质应用于水产品行业提供理论依据。

Antibacterial Activity and Mechanism of the Eucalyptus Oil against Four Microorganism in Aquatic Products

The antibacterial activity and antibacterial mechanism of the eucalyptus oil on the four microorganism of aquatic products in vitro was investigated in the study. Firstly, the antibacterial activity of four selected EOs including tea tree oil, eucalyptus oil, clove oil and mentha oil against four tested bacterial strains including Escherichia coli, Shewanella putrefaciens, Vibrio parahaemolyticus and Staphylococcus aureus were tested by means of agar diffusion and broth dilution methods, respectively. In which, the diameters of inhibition zone (DIZ) and minimal inhibitory concentration (MIC) were tested to evaluate the antibacterial activity of the EOs respectively. Furthermore, the antibacterial mechanism of eucalyptus oil against the model bacteria including Gram-negative S. putrefaciens and Gram-positive S. aureus was deeply investigated. In the mechanism researching experiment, scanning electron microscopy (SEM), transmission electron microscopy (TEM), the electric conductivity, nucleic acid content and the intracellular ATP content at MIC were tested to determine cell membrane permeability, membrane integrity and cell physiological function, respectively. The results showed that the diameters of inhibition zone of eucalyptus oil against Escherichia coli, Shewanella putrefaciens, Vibrio parahaemolyticus and Staphylococcus aureus were 33.33, 27.87, 38.88, 39.61 mm, respectively. The MIC values of Escherichia coli, Shewanella putrefaciens, Vibrio parahaemolyticus and Staphylococcus aureus were 1.00, 1.25, 0.75, 0.63 μL/mL, respectively. Eucalyptus oil performed the strongest antibacterial performance to all tested strains The bacteria cells morphology and ultrastructure were apparently damaged by eucalyptus oil, the electric conductivity and the optical density (OD₂₆₀) value of the treated bacterial increased, meanwhile, the intracellular ATP content of the treated bacterial decreased. It could be concluded that the bacteria cells membrane permeability, integrity and cell physiological function were damaged when bacteria cells were exposed to the eucalyptus oil at MIC. From the study referred above, it was demonstrated that the cell membrane was affected by eucalyptus oil, resulting in a loss of cell homeostasis. The experiment will provide a theoretical basis for the application of eucalyptus oil as a natural antibacterial substance in aquatic products industry.