micro lab 24 background

gamma and ultraviolet

two forms of radiation used for killing microorganisms.

Gama

radiation that has it’s biggest impact when it collides with molecules in the cell, creating free radicals, which are toxic. (A form of Ionizing radiation).

Ultraviolet

radiation that primarily kills by damaging DNA and RNA by effecting bonding relationships within the molecule, such as dimers, which can lead to mutations. (Also known as non-ionizing radiation)

dimers

bonds between two adjacent pyrimidines in the DNA strand.

those are the wavelengths that are absorbed the most by DNA.

Why are wavelengths between 200 and 290 nm considered the most lethal?

100-280 nm

Exposure to a large amount of UV-C light (___-___nm) will cause more damage than cell systems can repair, leading to cell death.

sterility

For a method to achieve ____, it has to destroy spores and the most difficult to kill microbes.

penetrating ability

One of the biggest limitations in the use of UV light as a disinfecting or sterilizing method is its poor ______ _____.

surfaces, in air purifiers, or in drinking water

Ultraviolet light is mainly used for killing microbes on ____, _____, or _______.

plastic, glass, and many other materials

Ultraviolet light will not go through:

eyes and skin

UV light is very damaging to the ___ and ___.

254 nm

germicidal lamp emits a ___ nm light.

germicidal lamp

viable for killing microbes in the air and on surfaces such as inside transfer hoods for tissue culture, clean rooms, and operating rooms.

Materials needed

ultraviolet lamp

3×5 index cards or half sheets of paper

Box or shield to cover lamp

3 nutrient agar plates

inoculating loop or swab

Bunsen burner and striker

gloves