title: The role and synergistic effect of the light irradiation and H2O2 in photocatalytic inactivation of Escherichia coli.
abstract: Inactivation of Escherichia coli K-12 was conducted by applying a continuous supplying of commercial H2O2 to mimic the H2O2 production in a photocatalytic system, and the contribution of H2O2 in photocatalytic inactivation was investigated using a modified "partition system" and five E. coli mutants. The concentration of exogenous H2O2 required for complete inactivation of bacterial cells was much higher than that produced in-situ in common photocatalytic system, indicating that H2O2 alone plays a minor role in photocatalytic inactivation. However, the concentration of exogenously produced H2O2 required for effective inactivation of E. coli K-12 was much lower when the light irradiation was applied. To further investigate the possible physiological changes, inactivation of E. coli BW25113 (the parental strain), and its corresponding isogenic single-gene deletion mutants with light pretreatment was compared. The results indicate that light irradiation increases the bacterial intracellular Fe(2+) level and favors hydroxyl radical (OH) production via the catalytic reaction of Fe(2+), leading to increase in DNA damage. Moreover, the results indicate that the properties of light source, such as intensity and major emission wavelength, may alter the physiology of bacterial cells and affect the susceptibility to in-situ resultant H2O2 in the photocatalytic inactivation processes, leading to significant influence on the photocatalytic inactivation efficiencies of E. coli K-12.
authors.affiliation: School of Life Sciences, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong Special Administrative Region.
authors.forename: Tsz Wai
authors.initials: TW
authors.lastname: Ng
authors.affiliation: State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China. Electronic address: antc99@gig.ac.cn.
authors.forename: Taicheng
authors.initials: T
authors.lastname: An
authors.affiliation: State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China.
authors.forename: Guiying
authors.initials: G
authors.lastname: Li
authors.affiliation: Department of Science and Environmental Studies, The Hong Kong Institute of Education, Taipo, N.T., Hong Kong, China.
authors.forename: Wing Kei
authors.initials: WK
authors.lastname: Ho
authors.affiliation: School of Life Sciences, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong Special Administrative Region.
authors.forename: Ho Yin
authors.initials: HY
authors.lastname: Yip
authors.affiliation: Centre for Clean Environment and Energy, Griffith School of Environment, Griffith University, Queensland 4222, Australia.
authors.forename: Huijun
authors.initials: H
authors.lastname: Zhao
authors.affiliation: School of Life Sciences, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong Special Administrative Region. Electronic address: pkwong@cuhk.edu.hk.
authors.forename: Po Keung
authors.initials: PK
authors.lastname: Wong
mesh_terms: D002384:Catalysis; D004777:Environment; D048168:Escherichia coli K12 / Q000187:drug effects* / Q000235:genetics / Q000528:radiation effects*; D006861:Hydrogen Peroxide / Q000494:pharmacology*; D008027:Light; D050296:Microbial Viability / Q000187:drug effects* / Q000528:radiation effects*; D017384:Sequence Deletion / Q000187:drug effects / Q000528:radiation effects; D013045:Species Specificity; D013997:Time Factors
chemical_list: D006861:Hydrogen Peroxide
keywords: Escherichia coli; Photocatalytic inactivation mechanism; Reactive oxidative species; Single-gene deletion mutant