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Effects of UV Irradiation on Microbial Numbers and - University of - sas upenn

Effects of UV Irradiation on Microbial Numbers and - University of - sas upenn 2025

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The document outlines a laboratory experiment in a Molecular Biology course (BIOL 123) focused on the effects of UV irradiation on microbial populations, specifically two bacterial species: Serratia marcescens and Staphylococcus aureus. The objectives include understanding the impact of UV exposure duration on bacterial survival, learning enumeration techniques for microorganisms, and practicing dilution series calculations. The introduction discusses the nature of UV light, its categories (UVA, UVB, UVC), and their biological effects, including DNA damage leading to mutations and skin cancer. The lab procedures detail methods for counting bacteria using viable plate counts and assessing the protective effects of different SPF sunscreens against UV radiation. Students are expected to analyze results regarding bacterial survival rates and characteristics post-irradiation.

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What is the impact of UV irradiation on bacterial mutation rates?

Ultraviolet Irradiation can change the chemical structure of DNA and increase mutation frequency. The effects of mutagen on the oxidation activity of mutant LD-1 bacteria and the bioleaching capability of the bacteria on copper tailings are the main factors studied in this work.

How does UV light cause death of microbes?

Ultraviolet light can damage DNA molecules. If a cells DNA repair mechanisms cant keep up with the damage, mutations are the result. As harmful mutations accumulate, the cell eventually dies.

How does UV light cause mutation in bacteria?

UVA (and also UVB) radiation cause indirect damage to DNA via absorption of photons by non-DNA chromophores. This generates reactive oxygen species like singlet oxygen or hydrogen peroxide that oxidize the DNA bases causing mutations.

What does UV light do to organisms?

UV-B causes damage at the molecular level to the fundamental building block of life deoxyribonucleic acid (DNA). DNA readily absorbs UV-B radiation, which commonly changes the shape of the molecule in one of several ways. The illustration below illustrates one such change in shape due to exposure to UV-B radiation.

What is the effect of UV radiation on microbial cells?

UV-C radiation kills or inactivates microbes by damaging their deoxyribonucleic acid (DNA).

What does UV irradiation do?

UV irradiation is a disinfection method that uses short-wavelength ultraviolet radiation (UV-C) at 254nm that is harmful to microorganisms, killing them by disrupting their DNA and leaving them unable to perform vital cellular functions.

What is the effect of ultraviolet light on bacteria mortality?

One minute of exposure time to ultraviolet light resulted in 95-99% bacteria mortality. Therefore, complete mortality for Serratia marcescens is probably a little longer than one minute, but less than two minutes.

How does UV light affect microorganisms?

The commonly known effects of UV radiation on microbes are their nucleic acids damage. However, while UV can be used to inactivate microorganisms, they can also lead to evolution of more virulent strains.

Effects of UV Irradiation on Microbial Numbers and - University of - sas upenn 2025

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