Visible light damage to Escherichia coli in seawater: oxidative stress hypothesis
Autor: | M. Pommepuy, Michèle Gourmelon, J. Cillard |
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Rok vydání: | 1994 |
Předmět: |
Light
Oceans and Seas chemistry.chemical_element Photochemistry medicine.disease_cause Applied Microbiology and Biotechnology Microbiology Oxygen Superoxide dismutase chemistry.chemical_compound Bacterial Proteins medicine Escherichia coli Hydrogen peroxide chemistry.chemical_classification Reactive oxygen species biology Singlet oxygen Fatty Acids Free Radical Scavengers Oxidative Stress chemistry Biochemistry Catalase biology.protein Hydroxyl radical Reactive Oxygen Species Water Microbiology Oxidation-Reduction Oxidative stress |
Zdroj: | The Journal of applied bacteriology. 77(1) |
ISSN: | 0021-8847 |
Popis: | The effect of visible light on Escherichia coli H10407 in seawater microcosms was investigated. Light damage was estimated by loss of colony-forming ability. Illumination of E. coli suspended in oligotrophic seawater with visible light at an intensity of about 40 klux caused a drastic decrease of culturable bacteria which turned to a viable but non-culturable state. In seawater E. coli exhibited weak metabolic activity as estimated by 3H methyl-thymidine incorporation in the cell. Visible light did not significantly alter this metabolic activity and did not involve detectable oxidation of lipid membranes as evaluated by gas chromatography analysis of fatty acids. The involvement of oxygen and reactive oxygen species in phototoxicity was studied. A decrease of the toxic effect was observed when E. coli was exposed to visible light under anaerobic conditions. Scavengers of reactive oxygen species exhibited variable protective effects. beta-Carotene, a singlet oxygen scavenger, and superoxide dismutase were equally ineffective. On the other hand, catalase, which eliminates hydrogen peroxide and thiourea, a hydroxyl radical scavenger, showed a net protection. In addition desferrioxamine B, an iron chelator, was also effective in reducing phototoxicity, probably by preventing hydroxyl radical generation by decomposition of hydrogen peroxide in the presence of iron (Fenton reaction). Therefore, hydrogen peroxide and hydroxyl radical seem to be reactive intermediates of oxygen-dependent (type II) photosensitized reactions. |
Databáze: | OpenAIRE |
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