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 60s and 90s, respectively, in liquid culture. UVC-TiO2-PCO treatment for 6min 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 30-60min. S. typhimurium cells showed visible damage after 30min, which was confirmed using CLSM. All treated cells were stained red using propidium iodide under a fluorescent light.
Bibliographical noteFunding Information:
This study was supported by the Technology Development Program for Agriculture and Forestry , Ministry for Food, Agriculture, Forestry and Fisheries , Republic of Korea.
All Science Journal Classification (ASJC) codes
- Ecological Modelling
- Water Science and Technology
- Waste Management and Disposal