title: Bacterial inactivation in water, DNA strand breaking, and membrane damage induced by ultraviolet-assisted titanium dioxide photocatalysis.
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.
authors.affiliation: Department of Biotechnology, College of Life Science and Biotechnology, Yonsei University, Seoul 120-479, Republic of Korea.
authors.forename: Soohyun
authors.initials: S
authors.lastname: Kim
authors.forename: Kashif
authors.initials: K
authors.lastname: Ghafoor
authors.forename: Jooyoung
authors.initials: J
authors.lastname: Lee
authors.forename: Mei
authors.initials: M
authors.lastname: Feng
authors.forename: Jungyeon
authors.initials: J
authors.lastname: Hong
authors.forename: Dong-Un
authors.initials: DU
authors.lastname: Lee
authors.forename: Jiyong
authors.initials: J
authors.lastname: Park
mesh_terms: D002384:Catalysis / Q000528:radiation effects; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism* / Q000528:radiation effects; D053903:DNA Breaks, Double-Stranded / Q000187:drug effects / Q000528:radiation effects*; D004269:DNA, Bacterial / Q000378:metabolism; D019453:Escherichia coli O157 / Q000187:drug effects / Q000235:genetics / Q000528:radiation effects* / Q000648:ultrastructure; D016680:Genome, Bacterial / Q000235:genetics; D008089:Listeria monocytogenes / Q000187:drug effects / Q000528:radiation effects / Q000648:ultrastructure; D050296:Microbial Viability / Q000187:drug effects / Q000528:radiation effects*; D010084:Oxidation-Reduction / Q000187:drug effects / Q000528:radiation effects; D010957:Plasmids / Q000378:metabolism; D012486:Salmonella typhimurium / Q000187:drug effects / Q000528:radiation effects / Q000648:ultrastructure; D014025:Titanium / Q000494:pharmacology*; D014466:Ultraviolet Rays; D014871:Water Microbiology
chemical_list: D004269:DNA, Bacterial; C009495:titanium dioxide; D014025:Titanium
keywords: Bacterial membrane damage; DNA strand breaking activity; Pathogenic bacteria; Titanium dioxide; UV-assisted photocatalytic reaction