title: Relative effectiveness of the 300--320 NM spectral region on sunlight for the production of primary lethal damage in E. coli cells.
abstract: Cell inactivation by sunlight exposure has been studied in E. coli CSR 603 (uvrA recA phr), a K12 derivative which is deficient in all known repair systems. Under suitable conditions, unfiltered sunlight inactivates these cells to 10(-3) survival within 30 sec. The effects of unfiltered sunlight have been compared with those of sunlight filtered through 1-cm layers of aqueous caffeine solutions ranging in concentration from 1 to 20 mg/ml. In the wavelength region of solar emission below 320 nm, which is most critical for DNA damage, the transmission of these liquid filters changes from 10 to 90% within 8-nm intervals. Thus our results permit minimum estimates for the fraction of lethal lesions produced by the solar spectrum below certain wavelenghts. In an experiment analyzed in this manner more than 80% of primary lethal lesions are caused by wavelengths less than 321 nm, and more than 50% by wavelengths less than 306 nm, while the contribution of wavelengths greater than 380 nm to primary lethal damage is below 1%.
mesh_terms: D004260:DNA Repair; D004269:DNA, Bacterial / Q000528:radiation effects*; D004307:Dose-Response Relationship, Radiation; D004926:Escherichia coli / Q000235:genetics* / Q000528:radiation effects; D010641:Phenotype; D013472:Sunlight; D014466:Ultraviolet Rays
chemical_list: D004269:DNA, Bacterial