Cellular injuries upon exposure of Escherichia coli and Lactobacillus rhamnosus to high-intensity ultrasound
Cellular injuries upon exposure of Escherichia coli and Lactobacillus rhamnosus to high-intensity ultrasound
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DOI：
10.1111/j.1365-2672.2005.02619.x
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发表时间：
2005-01-01
影响因子：
4
通讯作者：
Knorr, D
中科院分区：
文献类型：
--
作者：
Ananta, E;Voigt, D;Knorr, D
目的：利用经典平板计数技术和流式细胞术检测高强度超声治疗对大肠杆菌（革兰氏阴性菌）和鼠李糖乳杆菌（革兰氏阳性菌）细胞损伤的影响。方法与结果：平板计数结果显示，大肠杆菌（d值8.3 min）对超声强度（20 kHz, 17.6 W）的响应远高于鼠李糖乳杆菌（d值18.1 min）。染料前体羧基荧光素二乙酸酯（carboxyfluorescein diacetate, cFDA）能在革兰氏阳性菌鼠李糖（L. rhamnosus）完整细胞的细胞质膜上自由扩散，使其在细胞内酶促转化并发出绿色荧光。相比之下，代表革兰氏阴性菌的大肠杆菌的外膜的存在显然阻止了活力标记cFDA的渗透。超声波在大肠杆菌上的应用使得越来越多的大肠杆菌外膜崩解，这使得cFDA能够穿透并在细胞内进行酶转化和积累。在评估的两种生物体中，只有一小部分人群在暴露于超声长达20分钟后被碘化丙啶标记。在实验条件下，超声波对细胞质膜没有明显的影响，尽管根据平板计数结果，存在活力损失。结论：超声诱导细胞死亡，可能与膜损伤无关。本研究的意义和影响：细菌素旨在破坏细胞质膜的稳定性，但受到外膜的抑制，因此可以通过超声辅助外膜的物理破坏来克服细菌素使用的局限性。
Aims: To examine cellular injuries occurring in cells of Escherichia coli (Gram-negative bacteria) and Lactobacillus rhamnosus (Gram-positive bacteria) in response to a high-intensity ultrasound treatment using classical plate count technique and flow cytometry.Method and Results: According to plate count results, E. coli (D-value 8.3 min) was far more sensitive than L. rhamnosus (D-value 18.1 min) in their response to the ultrasound intensity applied (20 kHz, 17.6 W). The dye precursor carboxyfluorescein diacetate (cFDA) could freely diffuse across the cytoplasmic membrane of intact cells of Gram-positive bacteria L. rhamnosus, resulting in its intracellular enzymatic conversion and emission of green fluorescence. In contrast, the presence of an outer membrane on E. coli, which represents the class of Gram-negative bacteria, apparently disabled the penetration of viability marker cFDA. Ultrasound application on E. coli yielded in an increasing population with disintegrated outer membrane, which allowed penetration of cFDA and its intracellular enzymatic conversion as well as accumulation. In both organisms evaluated only a small population was labelled by propidium iodide upon exposure to ultrasound for up to 20 min. Within the experimental conditions investigated ultrasound did not considerably affect the cytoplasmic membrane, although according to plate count results viability loss occurred.Conclusions: The results compiled suggest, that ultrasound induced cell death, which may not be related to membrane damage.Significance and Impact of the Study: Limitation on the use of bacteriocins, which are aimed on destabilization of cytoplasmic membrane but inhibited by the outer membrane, could be overcome by ultrasound-assisted physical disruption of the outer membrane.