A bacterial DNA repair test evaluating the genotoxicity of light sources

Silvio De Flora, Anna Camoirano, Alberto Izzotti, Carlo Bennicelli

Research output: Contribution to journalArticlepeer-review


A DNA repair test was used in order to assess its applicability for detecting the genotoxicity of sunlight and of the light emitted by halogen lamps and fluorescent lamps. This experimental system compares the lethality of test agents in the Escherichia coli wild-type WP2 and its isogenic counterparts lacking, either individually or in combination, various DNA repair mechanisms. DNA repair-deficient strains included WP2uvrA (uvrA-), WP67 (uvrA- polA-), CM561 (lexA-), CM571 (recA-), WP100 (uvrA- recA-), and CM871 (uvrA- recA- lexA-). All light sources produced a substantial killing of repair-deficient strains, with a maximum activity in the triple mutant CM871, at doses that did not affect survival of the wild type. The genotoxicity of uncovered quartz halogen bulbs was particularly potent, compared to fluorescent lamps and sunlight. Moreover, the mechanisms involved in repairing the DNA damage induced by halogen lamps were similar to those of a 254 nm UV source. The spectrum of genetic damage produced by sunlight and fluorescent lamps was conversely more comparable to that of a 365 nm UV source. These data demonstrated a harmful emission of appreciable amounts of genotoxic far-UV wavelengths by halogen lamps, thereby confirming our previous results in the his-Salmonella typhimurium mutagenicity test. Genotoxicity of halogen lamps could be easily prevented in both experimental systems by suitable glass or plastic covers. Compared to the mutagenicity end point, the differential lethality end point provided even more clear-cut results in detecting the DNA-damaging ability of all light sources. Moreover, parallel assays provided evidence that the bacterial DNA repair test was far more sensitive than the mutagenicity test in evaluating the genotoxicity of the light produced by halogen lamps. On the whole, the DNA repair test in E. coli is even simpler and faster (24 vs. 48 h) than the Salmonella mutagenicity test, and compares favorably in terms of sensitivity to genotoxic light sources.

Original languageEnglish
Pages (from-to)116-122
Number of pages7
JournalToxicology Mechanisms and Methods
Issue number2
Publication statusPublished - 1991


  • DNA repair
  • Escherichia coli
  • Fluorescent lamps
  • Genotoxicity
  • Halogen lamps
  • Mutagenicity
  • Salmonella typhimurium
  • Solar irradiation
  • Ultraviolet light

ASJC Scopus subject areas

  • Toxicology
  • Health, Toxicology and Mutagenesis


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