• Question: How does the UV light kill bacteria?

    Asked by Lucy to Richard on 10 Mar 2015.
    • Photo: Richard Simons

      Richard Simons answered on 10 Mar 2015:

      Ultraviolet light is a high energy version of the visible light that our bodies have evolved to use for vision.
      Because of its high energy the UV can penetrate the cell and interact with the DNA of a bacterium (a single bacteria cell). This interaction causes an alteration in the DNA of the bacterium, leaving it unable to replicate. Bacterial infection requires millions of bacteria in order to attack, and for that they must be able to reproduce.
      If a bacterium cannot reproduce, it cannot infect.

      If you want the ‘nuts and bolts’ definition, the UV photon causes two thymine (T bases) in the DNA helix to bond together, stopping the DNA replication process.

      A similar process occurs in our skin if we spend too much time in the sun without sun cream on

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