title: Contribution of reactive oxygen species to UV-B-induced damage in bacteria.
abstract: The present work aimed to identify the reactive oxygen species (ROS) produced during UV-B exposure and their biochemical targets, in a set of bacterial isolates displaying different UV susceptibilities. For that, specific exogenous ROS scavengers (catalase/CAT, superoxide dismutase/SOD, sodium azide and mannitol) were used. Biological effects were assessed from total bacterial number, colony counts and heterotrophic activity (glucose uptake and respiration). DNA strand breakage, ROS generation, oxidative damage to proteins and lipids were used as markers of oxidative stress. Sodium azide conferred a statistically significant protection in terms of lipid oxidation and cell survival, suggesting that singlet oxygen might play an important role in UV-B induced cell inactivation. Mannitol exerted a significant protection against DNA strand breakage and protein carbonylation, assigning hydroxyl radicals to DNA and protein damage. The addition of exogenous CAT and SOD significantly protected the capacity for glucose uptake and respiration, suggesting that superoxide and H(2)O(2) are involved in the impairment of activity during UV-B exposure. The observation that amendment with ROS scavengers can sometimes also exert a pro-oxidant effect suggests that the intracellular oxidant status of the cell ultimately determines the efficiency of antioxidant defenses.
authors.affiliation: Department of Biology & CESAM, University of Aveiro, Campus Universitário de Santiago, 3810-193 Aveiro, Portugal.
authors.forename: Ana L
authors.initials: AL
authors.lastname: Santos
authors.forename: Newton C M
authors.initials: NC
authors.lastname: Gomes
authors.forename: Isabel
authors.initials: I
authors.lastname: Henriques
authors.forename: Adelaide
authors.initials: A
authors.lastname: Almeida
authors.forename: António
authors.initials: A
authors.lastname: Correia
authors.forename: Ângela
authors.initials: Â
authors.lastname: Cunha
mesh_terms: D001419:Bacteria / Q000166:cytology / Q000187:drug effects / Q000378:metabolism* / Q000528:radiation effects*; D019069:Cell Respiration / Q000187:drug effects / Q000528:radiation effects; D016166:Free Radical Scavengers / Q000494:pharmacology; D005947:Glucose / Q000378:metabolism; D018384:Oxidative Stress / Q000187:drug effects / Q000528:radiation effects; D017382:Reactive Oxygen Species / Q000378:metabolism*; D017392:Thiobarbituric Acid Reactive Substances / Q000378:metabolism; D014466:Ultraviolet Rays / Q000009:adverse effects*
chemical_list: D016166:Free Radical Scavengers; D017382:Reactive Oxygen Species; D017392:Thiobarbituric Acid Reactive Substances; D005947:Glucose