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Methods:UV Sensitivity Assay

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UV irradiation causes DNA damage that must be repaired in order for replication of the chromosome to occur. This assay is used to determine whether a strain's recombinational repair mechanisms have been compromised. Failure to repair the breaks will lead to induction of the SOS Response and a decrease in cell viability.

Materials Needed

  • UV light source
  • Incubator
  • Control Strains:
    • Recombination proficient control (like MG1655)
    • Recombination-deficient control (like DH5&alpha')


  1. Grow cells to A600 = 0.4
  2. Plate serial dilutions onto LB plates
  3. Grow for 30 minutes
  4. Expose plates to UV light
  5. Incubate overnight (up to 72 hours)
  6. Count colonies


User notes

  • Protocol taken from Lopez et al. (2005)[1]


See Help:References for how to manage references in EcoliWiki.

  1. Lopez, CR et al. (2005) A role for topoisomerase III in a recombination pathway alternative to RuvABC. Mol. Microbiol. 58 80-101 PubMed EcoliWiki page