Bacterial inactivation in water,DNA strand breaking,and membrane damage induced by ultraviolet-assisted titanium dioxide photocatalysis |
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Authors: | Soohyun Kim Kashif Ghafoor Jooyoung Lee Mei Feng Jungyeon Hong Dong-Un Lee Jiyong Park |
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Affiliation: | 1. Department of Biotechnology, College of Life Science and Biotechnology, Yonsei University, Seoul 120-479, Republic of Korea;2. Department of Food Science and Nutrition, College of Food and Agricultural Sciences, King Saud University, Riyadh, Saudi Arabia;3. Department of Food Science and Technology, Chung-Ang University, Anseong 456-756, Republic of Korea |
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Abstract: | The effects of UV-assisted TiO2-photocatalytic oxidation (PCO) inactivation of pathogenic bacteria (Escherichia coli O157:H7, Listeria monocytogenes, Salmonella typhimurium) in a liquid culture using different domains of UV irradiation (A, B and C) were evaluated. Structural changes in super-coiled plasmid DNA (pUC19) and genomic DNA of E. coli were observed using gel electrophoresis to demonstrate the photodynamic DNA strand breaking activity of UV-assisted TiO2-PCO. Membrane damage in bacterial cells was observed using both a scanning electron microscope (SEM) and a confocal laser scanning microscope (CLSM). Both UVC-TiO2-PCO and UVC alone resulted in an earlier bactericidal phase (initial counts of approximately 6 log CFU/mL) in 60 s and 90 s, respectively, in liquid culture. UVC-TiO2-PCO treatment for 6 min converted all plasmid DNA to the linear form; however, under UVC irradiation alone, super-coiled DNA remained. Prolonged UVC-TiO2-PCO treatment resulted in structural changes in genomic DNA from E. coli. SEM observations revealed that bacteria suffered severe visible cell damage after UVC-TiO2-PCO treatment for 30–60 min. S. typhimurium cells showed visible damage after 30 min, which was confirmed using CLSM. All treated cells were stained red using propidium iodide under a fluorescent light. |
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Keywords: | Titanium dioxide UV-assisted photocatalytic reaction Pathogenic bacteria DNA strand breaking activity Bacterial membrane damage |
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