超高压对大肠杆菌O157:H7细胞膜的损伤效应

本研究旨在揭示超高压对食源性致病微生物大肠杆菌O157:H7细胞膜的损伤。研究了200、400、500 MPa不同压力对大肠杆菌O157:H7的灭活作用,通过对菌体细胞核酸类物质、钾离子和镁离子泄漏量、碘化丙啶(propidium iodide,PI)摄入量、细胞膜Na+/K+-ATP酶和Ca~(2+)/Mg~(2+)-ATP酶活性变化的分析研究,评价不同超高压处理压力对大肠杆菌O157:H7膜损伤效应。结果表明,经200、400 MPa压力处理5 min后,大肠杆菌O157:H7菌落总数由初始8.8(lg(CFU/m L))分别下降至8.2(lg(CFU/m L))和6.3(lg(CFU/m L)),500 MPa压力处理后,大肠杆菌O157:H7全部死亡。压力升高,细菌细胞内核酸类物质、K+、Mg~(2+)离子泄漏量、PI摄入量均显著增加,细胞膜上Na+/K+-ATP酶和Ca~(2+)/Mg~(2+)-ATP酶活性显著降低。Ca~(2+)/Mg~(2+)-ATP酶对压力的敏感性更强,500 MPa处理组该酶活性几乎完全丧失。超高压处理引起大肠杆菌O157:H7细胞膜产生显著损伤,细胞膜上Ca~(2+)/Mg~(2+)-ATP酶的失活是导致大肠杆菌O157:H7死亡的主要原因。

Cell Membrane Injury of Escherichia coli O157:H7 Caused by Hydrostatic Pressure

This study investigated the membrane injury of Escherichia coli O157:H7 cells exposed to high hydrostatic pressure. Different pressure levels (200, 400 and 500 MPa) were used to evaluate the inactivation of the bacteria. The leakage of nucleic acids, K+ and Mg2+, and propidium iodide (PI) intake of the cells, as well as changes in Na+/K+-ATPase and Ca2+/Mg2+-ATPase activities were determined after pressure treatment. Results indicated that, after 200 and 400 MPa treatments for 5 min, the number of viable cells decreased from an initial level of 8.8 to 8.2 and 6.3 (lg(CFU/mL)), respectively. When treated at 500 MPa, no viable cells were detected on plate count agar. As the pressure level rose, the leakage of intratracellular constituents and the fluorescence (OD) of PI intake increased significantly and both enzyme activities significantly decreased. Ca2+/Mg2+-ATPase was more sensitive to pressure than Na+/K+-ATPase, and the enzyme activities were almost completely inactivated after pressurization at 500 MPa. High pressure treatment caused obvious damage to the membrane of E. coli O157:H7 cells. The major cause of E. coli O157:H7 death after high hydrostatic pressure treatment was the inactivation of Ca2+/Mg2+-ATPase.