title: UV-A oxidative damage modified by environmental conditions in Escherichia coli.
abstract: The effect of sublethal fluences (50-200 kJ m-2) of UV-A radiation (320-400 nm) in bacterial cells is a transient growth inhibition related to photo-modified tRNA and is associated with changes in membrane structure and function. Higher UV-A fluences result in cell death due to the production of reactive oxygen species, so far undetected at sublethal doses. Oxidative mechanisms of toxicity induced by 120 kJ m-2 UV-A radiation can be recorded by ultra-weak chemiluminescence, useful in quantifying oxidative reactions. When Escherichia coli was exposed to UV-A stress at a fluence rate equivalent to that of the Sun in the biosphere (33 W m-2), chemiluminescence levels were proportional to the photodamage. Chemiluminescence and photo-damage are linearly proportional and dependent on environmental conditions of the cells. It is postulated that in addition to tRNA photo-modification, UV-A alters the membrane structure of E. coli by oxidative damage, since changes in the membrane structure under different environmental conditions play a key role in the cell's response to UV-A injury.
authors.affiliation: Departamento de Radiobiología, Comisión Nacional de Energía Atómica, Buenos Aires, Argentina.
authors.forename: R A
authors.initials: RA
authors.lastname: Pizarro
mesh_terms: D002462:Cell Membrane / Q000187:drug effects / Q000201:enzymology; D004926:Escherichia coli / Q000254:growth & development / Q000528:radiation effects*; D000431:Ethanol / Q000494:pharmacology; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D008163:Luminescent Measurements; D009584:Nitrogen / Q000494:pharmacology; D010084:Oxidation-Reduction; D010545:Peroxides / Q000737:chemistry; D013385:Succinate Dehydrogenase / Q000378:metabolism; D013696:Temperature; D014466:Ultraviolet Rays
chemical_list: D010545:Peroxides; D000431:Ethanol; D007770:L-Lactate Dehydrogenase; D013385:Succinate Dehydrogenase; D009584:Nitrogen