title: Evaluation of Ultrasound-Induced Damage to Escherichia coli and Staphylococcus aureus by Flow Cytometry and Transmission Electron Microscopy.
abstract: As a nonthermal sterilization technique, ultrasound has attracted great interest in the field of food preservation. In this study, flow cytometry and transmission electron microscopy were employed to investigate ultrasound-induced damage to Escherichia coli and Staphylococcus aureus. For flow cytometry studies, single staining with propidium iodide (PI) or carboxyfluorescein diacetate (cFDA) revealed that ultrasound treatment caused cell death by compromising membrane integrity, inactivating intracellular esterases, and inhibiting metabolic performance. The results showed that ultrasound damage was independent of initial bacterial concentrations, while the mechanism of cellular damage differed according to the bacterial species. For the Gram-negative bacterium E. coli, ultrasound worked first on the outer membrane rather than the cytoplasmic membrane. Based on the double-staining results, we inferred that ultrasound treatment might be an all-or-nothing process: cells ruptured and disintegrated by ultrasound cannot be revived, which can be considered an advantage of ultrasound over other nonthermal techniques. Transmission electron microscopy studies revealed that the mechanism of ultrasound-induced damage was multitarget inactivation, involving the cell wall, cytoplasmic membrane, and inner structure. Understanding of the irreversible antibacterial action of ultrasound has great significance for its further utilization in the food industry.
authors.affiliation: Department of Food Science and Nutrition, Zhejiang Key Laboratory for Agro-Food Processing, Zhejiang University, Hangzhou, Zhejiang, China.
authors.forename: Jiao
authors.initials: J
authors.lastname: Li
authors.affiliation: Department of Medical Biomaterials Engineering, Kangwon National University, Gangwon, Chuncheon, Republic of Korea.
authors.forename: Juhee
authors.initials: J
authors.lastname: Ahn
authors.affiliation: Department of Food Science and Nutrition, Zhejiang Key Laboratory for Agro-Food Processing, Zhejiang University, Hangzhou, Zhejiang, China.
authors.forename: Donghong
authors.initials: D
authors.lastname: Liu
authors.affiliation: Department of Food Science and Nutrition, Zhejiang Key Laboratory for Agro-Food Processing, Zhejiang University, Hangzhou, Zhejiang, China.
authors.forename: Shiguo
authors.initials: S
authors.lastname: Chen
authors.affiliation: Department of Food Science and Nutrition, Zhejiang Key Laboratory for Agro-Food Processing, Zhejiang University, Hangzhou, Zhejiang, China.
authors.forename: Xingqian
authors.initials: X
authors.lastname: Ye
authors.affiliation: Department of Food Science and Nutrition, Zhejiang Key Laboratory for Agro-Food Processing, Zhejiang University, Hangzhou, Zhejiang, China tding@zju.edu.cn.
authors.forename: Tian
authors.initials: T
authors.lastname: Ding
mesh_terms: D002462:Cell Membrane / Q000528:radiation effects; D004203:Disinfection / Q000379:methods; D004926:Escherichia coli / Q000502:physiology / Q000528:radiation effects* / Q000648:ultrastructure*; D005434:Flow Cytometry; D005456:Fluorescent Dyes / Q000032:analysis; D053858:Metabolic Networks and Pathways / Q000528:radiation effects; D050296:Microbial Viability / Q000528:radiation effects; D046529:Microscopy, Electron, Transmission; D013010:Sonication / Q000379:methods; D013194:Staining and Labeling / Q000379:methods; D013211:Staphylococcus aureus / Q000502:physiology / Q000528:radiation effects* / Q000648:ultrastructure*; D000069453:Ultrasonic Waves
chemical_list: D005456:Fluorescent Dyes