百里醌对阪崎克罗诺肠杆菌的抑制作用

为探究百里醌对阪崎克罗诺肠杆菌的抑制作用及可能的抑制机理，检测了百里醌对阪崎克罗诺肠杆菌的最 小抑菌浓度（minimal inhibitory concentrations，MIC）及对其生长动力学模型的影响，并测定百里醌处理后阪崎肠 杆菌胞内ATP浓度、胞内pH值、膜电位、细胞膜完整性的变化，最后利用场发射扫描电子显微镜观察细胞形态的 改变。结果表明：百里醌对阪崎克罗诺肠杆菌的MIC为0.3～0.6 mg/mL；百里醌使阪崎克罗诺肠杆菌的生长迟滞期 延长，最大生长速率减小；百里醌影响了阪崎克罗诺肠杆菌细胞膜的通透性，表现为：质量浓度为MIC和2×MIC 的百里醌使细胞内ATP浓度由6.52 μmol/L分别降低为0.27 μmol/L和0.17 μmol/L，胞内pH值分别由5.69降低为5.22和 4.99，细胞膜完整菌体比例分别降低至80%和22%，引起细胞膜膜电位超极化；场发射扫描电子显微镜观测表明百 里醌使阪崎克罗诺肠杆菌细胞膜褶皱，菌体干瘪。综上所述，百里醌是通过影响细胞膜通透性和改变细胞形态抑制 阪崎克罗诺肠杆菌。这些结果表明百里醌有潜力作为控制阪崎克罗诺肠杆菌的天然抑菌剂应用于食品中。

Antimicrobial Activity of Thymoquinone against Cronobacter sakazakii

The objective of the present study was to evaluate the effectiveness of thymoquinone (TQ) against Cronobacter sakazakii strains. The minimum inhibitory concentration (MIC) of TQ against C. sakazakii and its effect on microbial growth kinetics were determined. Changes in intracellular ATP concentration, intracellular pH (pHin), membrane potential and membrane integrity were measured to elucidate the possible antimicrobial mechanism. Cell morphology changes were also observed under a field emission scanning electron microscope. The results showed that the MICs of TQ against C. sakazakii strains ranged from 0.3 to 0.6 mg/mL, and TQ exposure resulted in a longer lag phase and lower specific growth rate compared to the control. TQ affected the cell membrane permeability of C. sakazakii, as evidenced by a reduction in intracellular ATP concentration from 6.52 to 0.27 and 0.17 μmol/L and a decrease in pHin from 5.69 to 5.22 and 4.99 at MIC and 2 × MIC, respectively. TQ at both tested concentrations caused 80% and 22% reduction in cell integrity, respectively. In addition, cells treated with TQ showed hyperpolarized cell membrane. Field emission scanning electron microscopy illustrated that C. sakazakii cells exposed to TQ exhibited a more wrinkled surface compared with the smooth surface of untreated cells. In conclusion, TQ exerts its antimicrobial action partly by causing excessive permeability of the cell membrane and changing cell morphology. These findings suggest that TQ has potential application in controlling C. sakazakii in foods.