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Lab Exercise 30 Lethal Effects of Ultraviolet light

Background. Objective : To assess the effect of UV light on Bacillus megatarium and Staphylococcus aureusBackground: There are two forms radiation that can be lethal to bacteria: Ionizing radiation (x-rays or gamma radiation )carries enough energy to remove electrons from molecules in a

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Lab Exercise 30 Lethal Effects of Ultraviolet light

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    1. Lab Exercise 30 Lethal Effects of Ultraviolet light

    2. Background Objective : To assess the effect of UV light on Bacillus megatarium and Staphylococcus aureus Background: There are two forms radiation that can be lethal to bacteria: Ionizing radiation (x-rays or gamma radiation )carries enough energy to remove electrons from molecules in a cell (ionization). Non-ionizing radiation ultraviolet (UV) light excites electrons in molecules. -The excitation of electrons in DNA molecules formation of extra bonds between adjacent pyrimidines (specifically thymine) in DNA. (pyrimidine dimers) -The cell often tries to repair pyrimidine dimers (S.O.S repair)before replication, but the repair mechanism can also lead to mutations as well. - UV does not penetrate surfaces ! - 260nm i------> most germicidal UV wavelength Both ionizing and nonionizing radiation are used to control the growth of microorganisms in clinical settings, the food industry and in laboratories.

    4. Lab Procedure overview Remove lid and place index card onto ½ of the plate and expose the plate to germicidal UV (260nm) light for an assigned amount of time (see figure 1). After UV exposure the plate will be closed and incubated for 24 hours. Figure 1

    5. Pre-lab Questions

    7. Background

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