以铜绿假单胞菌(Pseudomonas aeruginosa)为试验菌,探究牡丹花蕾提取物的抑菌活性及机理。利用琼脂滤纸片扩散法和微量稀释法评价抑菌活性;测定生长曲线、膜脂肪酸组成、膜蛋白荧光光谱、膜通透性及细胞形态变化来探究抑菌机理。牡丹花蕾提取物抑制铜绿假单胞菌生长,最低抑制浓度(minimum inhibitory concentration, MIC)和最低杀死浓度(minimum bactericidal concentration, MBC)分别为3.13和6.25 mg/mL。在MIC和MBC下,细胞膜饱和脂肪酸相对含量提高了6.06%和8.19%,而单不饱和脂肪酸相对含量降低了5.17%和6.91%,从而导致膜流动性降低;同时提取物降低膜蛋白Phe、Trp和Tyr荧光强度,表明膜蛋白构象改变,导致膜功能产生障碍。此外,提取物破坏膜完整性和增加膜通透性。牡丹花蕾提取物通过改变膜脂肪酸组成和膜蛋白构象并破坏膜完整性发挥抑菌作用,可作为防腐保鲜剂予以开发。
The aim of this study was to investigate the antibacterial activities and mechanisms of Paeonia suffruticosa Andr. buds extract against Pseudomonas aeruginosa. The antibacterial activities were evaluated by agar diffusion assay and microdilution method, and the mechanisms were investigated by determining the growth curves, membrane fatty acid composition, membrane protein fluorescence spectra and membrane permeability of cells, as well as changes in cell morphology. It was found that the growth of P. aeruginosa was inhibited by the extract, and the minimum inhibition concentration (MIC) and minimum bactericide concentration (MBC) were 3.13 and 6.25 mg/mL, respectively. The relative proportions of saturated fatty acids in cell membranes increased by 6.06% and 8.19% at MIC and MBC, respectively, while the relative proportions of monounsaturated fatty acid decreased by 5.17% and 6.91%, respectively, which resulted in a decrease in membrane fluidity. Moreover, the fluorescence intensities of Phe, Trp and Tyr residues in membrane proteins reduced, which indicated that the extract could change their conformations and cause membrane dysfunction. In addition, the extract could destroy the integrity of cell membrane and increase its permeability. In conclusion, Paeonia suffruticosa Andr. buds extract can be developed as a promising preservative.
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