RELATIVE EFFECTIVENESS OF THE 300-320 NM SPECTRAL REGION OF SUNLIGHT FOR THE PRODUCTION OF PRIMARY LETHAL DAMAGE IN ESCHERICHIA-COLI-CELLS

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 wavelengths. In an experiment analyzed in this manner more than 80% of primary lethal lesions are caused by wavelengths <312 nm, and more than 50% by wavelengths <306 nm, while the contribution of wavelengths >380 nm to primary lethal damage is below 1%. © 1979.