肉桂精油气相熏蒸金黄色葡萄球菌的抗菌机理

Antibacterial Mechanism of Cinnamon Essential Oil Vapor Fumigation against Staphylococcus aureus

该研究主要探讨了肉桂精油的抗菌活性及其对金黄色葡萄球菌的抗菌机制,实验采用气相熏蒸法研究精油的气相抗菌活性,通过TEM、电导率实验、FT-IR、荧光光谱等方法探讨肉桂精油的气相抗菌机制。结果表明肉桂精油具有显著的气相抗菌活性,对金黄色葡萄球菌的最低抑菌浓度(MIC)为0.25μL/mL,最低杀菌浓度(MBC)为0.5μL/mL。TEM观察显示,经肉桂精油气熏后的金黄色葡萄球菌菌体细胞膜破损溶解,细胞皱缩,从而引起内容物外泄。电导率实验进一步表明气熏后的菌体细胞膜通透性提高,并通过测试OD260发现核酸外泄与精油浓度变化的正相关关系。通过FT-IR图与荧光光谱图,发现肉桂精油引起金黄色葡萄球菌菌体蛋白构象的变化,并通过分析酰胺Ⅰ带推测在气熏过程中菌体蛋白二级结构发生无序变化,以及通过荧光强度和波长峰位的变化判断肉桂精油气熏后菌体蛋白发生了改变,暴露出更多的发色基团。由此可见,肉桂精油气相熏蒸金黄色葡萄球菌可能的抑菌机理是改变菌体细胞膜通透性和形态,并改变了菌体蛋白的二级结构和三级结构。

The antibacterial function of the vapor-phase of the essential oil from Cinnamomum cassia(EOL)against Staphylococcus aureus(S.aureus)and the underlying mechanisms were investigated.Gas phase fumigation was used in the experiments to examine the antibacterial mechanism of gas-phase cinnamon essential oils by TEM,conductivity test,FT-IR spectroscopy,fluorescence spectroscopy and other methods were used to characterize the change of cellular membrane after treated by essential oil through gas phase fumigation method.The results showed that EOL had significant vapor-phase antibacterial activity with a MIC and MBC against S.aureus being 0.25μL/mL and 0.5μL/mL,respectively.TEM observations showed that the cell membrane of S.aureus was damaged and dissolved after being fumigated by Cinnamomum essential oil,and the cells shrank,causing the contents to leak out.The conductivity experiments further confirmed that the cell membrane permeability of S.aureus was improved,and apositive correlation between nucleic acid leakage and the changes in the concentration of essential oil was found by measuring OD260.The FT-IR and fluorescence spectra showed the changes in protein conformation of S.aureus caused by the treatment with cinnamon essential oil.On the analysis of the amide I band,it was speculated that the secondary structure of bacterial proteins became more disordered in the process of fumigation.Based on the changes in fluorescence intensity and spectralpeak position,one could speculate that the bacterial proteins had changed after the cinnamon essential oil fumigation,leading to more exposed chromophores.Accordingly,the possible antibacterial mechanism of cinnamon essential oil fumigation against S.aureus was related to the changes in the cell membrane permeability and morphology,and secondary and tertiary structures of bacterial proteins.