title: Growth conditions influence UVB sensitivity and oxidative damage in an estuarine bacterial isolate.
abstract: The dose-dependent variation of oxidative cellular damage imposed by UVB exposure in a representative estuarine bacterial strain, Pseudomonas sp. NT5I1.2B, was studied at different growth phases (mid-exponential, late-exponential, and stationary), growth temperatures (15 °C and 25 °C) and growth media (nutrient-rich Tryptic Soy Broth [TSB] and nutrient-poor M9). Survival and markers of oxidative damage (lipid peroxidation, protein carbonylation, DNA strand breakage, and DNA-protein cross-links) were monitored during exposure to increasing UVB doses (0-60 kJ m(-2)). Oxidative damage did not follow a clear linear dose-dependent pattern, particularly at high UVB doses (>10 kJ m(-2)), suggesting a dynamic interaction between damage induction and repair during irradiation and/or saturation of oxidative damage. Survival of stationary phase cells generally exceeded that of exponential phase cells by up to 33.5 times; the latter displayed enhanced levels of DNA-protein cross-links (up to 15.6-fold) and protein carbonylation (up to 6.0-fold). Survival of mid-exponential phase cells was generally higher at 15 °C than at 25 °C (up to 6.6-fold), which was accompanied by lower levels of DNA strand breaks (up to 4000-fold), suggesting a temperature effect on reactive oxygen species (ROS) generation and/or ROS interaction with cellular targets. Survival under medium-high UVB doses (>10 kJ m(-2)) was generally higher (up to 5.4-fold) in cells grown in TSB than in M9. These results highlight the influence of growth conditions preceding irradiation on the extent of oxidative damage induced by UVB exposure in bacteria.
authors.affiliation: Department of Biology & CESAM, University of Aveiro, 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: Angela
authors.initials: A
authors.lastname: Cunha
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism; D053960:DNA Breaks / Q000528:radiation effects; D004269:DNA, Bacterial / Q000235:genetics / Q000378:metabolism; D015227:Lipid Peroxidation / Q000528:radiation effects; D018384:Oxidative Stress; D011549:Pseudomonas / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism / Q000528:radiation effects*; D014466:Ultraviolet Rays
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial