The effects of ultra violet light on bacterial growth

Written by susan roberts
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The effects of ultra violet light on bacterial growth
Exposure to ultraviolet light damages bacterial DNA. (adn ? image by G.g1 from

Ultraviolet light, also called ultraviolet radiation or UV, is a portion of the electromagnetic spectrum between X-rays and visibility light. Ultraviolet light comes from natural and man-made sources, including the sun, halogen lights, tanning booths and germicidal lamps. With man-made sources you can control the factors of UV exposure and use it for a specific purpose such as impacting bacterial growth.


Short wavelength ultraviolet light can damage chemical bonds in the bacterial cells' DNA. With enough of the right kind of exposure, this damage occurs quickly so that the bacteria cannot replicate and repair fast enough. Eventually the bacteria is completely eradicated.

Slow Growth

Exposure to ultraviolet light may prohibit growth and reproduction in some, but not all, bacterial cells. This produces an effect of slowing the growth of the bacterial colony even though it may not completely get rid of the bacteria.

No Impact

The wrong wavelength, or incorrectly applied ultraviolet light, may have no impact on bacterial growth. For example, UV light damages or kills only what it touches directly. In water treatment plants, for example, the water flows through a UV system. If the flow rate through the system is too fast to allow adequate exposure to the ultraviolet light, then the bacteria growth will not be impacted at all.

Gene Mutation

If ultraviolet exposure doesn't kill or slow bacterial growth, it has the potential to damage cells just enough that they have enough time to partially repair and then permanently mutate. Gene mutation occurs in cancer formation, but it also occurs in bacterial growth.

Reduced Disease Outbreaks

With continuous UV exposure, such as when treating aquariums and air, ultraviolet radiation can reduce the likelihood of disease outbreaks. In air treatments, for example, a study submitted to the Centers for Disease Control and Prevention demonstrated that ultraviolet germicidal irradiation can reduce the risk of tuberculosis and other airborne diseases.

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