Photoinactivation of Eight Health-Relevant Bacterial Species: Determining the Importance of the Exogenous Indirect Mechanism.
It is presently unknown to what extent the endogenous direct, endogenous indirect, and exogenous indirect mechanisms contribute to bacterial photoinactivation in natural surface waters. In this study, we investigated the importance of the exogenous indirect mechanism by conducting photoinactivation experiments with eight health-relevant bacterial species (Bacteroides thetaiotaomicron, Campylobacter jejuni, Enterococcus faecalis, Escherichia coli K12, E. coli O157:H7, Salmonella enterica serovar Typhimurium LT2, Staphylococcus aureus, and Streptococcus bovis). We used three synthetic photosensitizers (methylene blue, rose bengal, and nitrite) and two model natural photosensitizers (Suwannee River natural organic matter and dissolved organic matter isolated from a wastewater treatment wetland) that generated singlet oxygen and hydroxyl radical. B. thetaiotaomicron had larger first order rate constants than all other organisms under all conditions tested. The presence of the synthetic photosensitizers generally enhanced photoinactivation of Gram-positive facultative anaerobes (Ent. faecalis, Staph. aureus, and Strep. bovis). Among Gram-negative bacteria, only methylene blue with E. coli K12 and rose bengal with C. jejuni showed an enhancing effect. The presence of model natural photosensitizers either reduced or did not affect photoinactivation rate constants. Our findings highlight the importance of the cellular membrane and photosensitizer properties in modulating the contribution of the exogenous indirect mechanism to the overall bacterial photoinactivation.
Department of Civil and Environmental Engineering, Stanford University , Stanford, California 94305, United States.|Engineering Research Center (ERC) for Re-inventing the Nation's Urban Water Infrastructure (ReNUWIt), Stanford, California 94305, United States.
Peter A
PA
Maraccini
Department of Civil & Environmental Engineering, University of California , Berkeley, California 94720-1710, United States.|Engineering Research Center (ERC) for Re-inventing the Nation's Urban Water Infrastructure (ReNUWIt), Stanford, California 94305, United States.
Jannis
J
Wenk
Department of Civil and Environmental Engineering, Stanford University , Stanford, California 94305, United States.|Engineering Research Center (ERC) for Re-inventing the Nation's Urban Water Infrastructure (ReNUWIt), Stanford, California 94305, United States.
Alexandria B
AB
Boehm
D006090:Gram-Negative Bacteria; D008751:Methylene Blue / Q000737:chemistry; D017319:Photosensitizing Agents / Q000737:chemistry; D012395:Rose Bengal; D013211:Staphylococcus aureus
D017319:Photosensitizing Agents; D012395:Rose Bengal; D008751:Methylene Blue