How to Kill Bacteria on Nutrient Agar
Nutrient agar is a nutrition substrate used in laboratories for the culturing of live bacteria and may sustain the microbial colony for a longer duration than needed. To prevent safety risks and contamination, the substrate medium must be sterilized of all microbes before being discarded. Hospitals and science labs have been increasingly using a special type of ultraviolet light in the C band of the ultraviolet light spectrum for sterilizing instruments and lab surfaces. Also known as UV-C light, this particular wavelength provides a fatal sunburn to all microbes without the need for toxic antibacterial chemicals, and is thoroughly efficient.
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Things You'll Need
- Hanging UV-C lamp and fixture with shield
- Eye-protection glasses rated for the blocking of ultraviolet C wavelength
- Microscope with lens power rating for viewing your particular microbes
- Microscope glass blank with glass specimen cover
- Cotton swab
Instructions
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Hang a 15-watt UV-C lamp fixture within 6 inches of the nutrient agar substrate containing the microbial colony.
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Put on a pair of sunglasses rated for the blockage of ultraviolet light in the C band. Wear the glasses every time you look in the direction of the lamp, even if you aren't looking directly at it.
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Turn on the lamp and leave the room, allowing the lamp to shine on the nutrient agar for about four to six hours without interruption.
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Turn the lamp off and, using a cotton swab, obtain a sample of your culture from the nutrient agar substrate and smear it onto a microscope slide, covering with a blank slide cover.
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Place the slide under your microscope and observe the specimen to verify that the colony has been destroyed. If some of the culture remains alive, turn the UV-C lamp on and leave overnight; then retest the culture.
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Once the colony has been destroyed, discard the substrate board according to scientifically agreed-upon protocols.
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Tips & Warnings
UV-C light can cause complete blindness within seconds of direct light exposure to the eyes. Never look at UV-C light without fixture shielding and wearing proper eye-protection equipment.
UV-C light destroys DNA, which is why it is so effective in killing microorganisms. This light also destroys DNA in the skin, leading to skin cancer. Always minimize your skin's exposure to C band ultraviolet light.
