title: Simultaneous irradiation with different wavelengths of ultraviolet light has synergistic bactericidal effect on Vibrio parahaemolyticus.
abstract: Ultraviolet (UV) irradiation is an increasingly used method of water disinfection. UV rays can be classified by wavelength into UVA (320-400 nm), UVB (280-320 nm), and UVC (<280 nm). We previously developed UVA sterilization equipment with a UVA light-emitting diode (LED). The aim of this study was to establish a new water disinfection procedure using the combined irradiation of the UVA-LED and another UV wavelength. An oxidative DNA product, 8-hydroxy-2'-deoxyguanosine (8-OHdG), increased after irradiation by UVA-LED alone, and the level of cyclobutane pyrimidine dimers (CPDs) was increased by UVC alone in Vibrio parahaemolyticus. Although sequential irradiation of UVA-LED and UVC-induced additional bactericidal effects, simultaneous irradiation with UVA-LED and UVC-induced bactericidal synergistic effects. The 8-OHdG and CPDs production showed no differences between sequential and simultaneous irradiation. Interestingly, the recovery of CPDs was delayed by simultaneous irradiation. The synergistic effect was absent in SOS response-deficient mutants, such as the recA and lexA strains. Because recA- and lexA-mediated SOS responses have crucial roles in a DNA repair pathway, the synergistic bactericidal effect produced by the simultaneous irradiation could depend on the suppression of the CPDs repair. The simultaneous irradiation of UVA-LED and UVC is a candidate new procedure for effective water disinfection.
authors.affiliation: Department of Preventive Environment and Nutrition, Institute of Health Biosciences, University of Tokushima Graduate School, Tokushima City, Tokushima, Japan.
authors.forename: Mutsumi
authors.initials: M
authors.lastname: Nakahashi
authors.forename: Kazuaki
authors.initials: K
authors.lastname: Mawatari
authors.forename: Akiko
authors.initials: A
authors.lastname: Hirata
authors.forename: Miki
authors.initials: M
authors.lastname: Maetani
authors.forename: Takaaki
authors.initials: T
authors.lastname: Shimohata
authors.forename: Takashi
authors.initials: T
authors.lastname: Uebanso
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Hamada
authors.forename: Masatake
authors.initials: M
authors.lastname: Akutagawa
authors.forename: Yousuke
authors.initials: Y
authors.lastname: Kinouchi
authors.forename: Akira
authors.initials: A
authors.lastname: Takahashi
mesh_terms: D000080242:8-Hydroxy-2'-Deoxyguanosine; D003849:Deoxyguanosine / Q000031:analogs & derivatives / Q000378:metabolism; D005798:Genes, Bacterial; D011740:Pyrimidine Dimers / Q000378:metabolism; D013014:SOS Response, Genetics; D014466:Ultraviolet Rays; D014736:Vibrio parahaemolyticus / Q000235:genetics / Q000528:radiation effects*
chemical_list: D011740:Pyrimidine Dimers; D000080242:8-Hydroxy-2'-Deoxyguanosine; D003849:Deoxyguanosine