micro lab (week 10) "control of microbial growth - effect of ultraviolet light"

When exposing your bacteria to UV light, how might the results differ if a UVA lamp compared to a UVC lamp?

UVA exposed plate would have more microbial growth

When UV radiation is applied to cells, it causes the formation of _____ _____ in the DNA helix. This can interfere with DNA ______, reducing the expression of important genes and potentially cause death of the cell.

abnormal bonds; replication

Which of the following DNA sequences would be the most likely to be damaged by UV radiation? a) ATGCACATGA b) CTTGAATTAA c) GACACGTAGA d) GCATGACATA

b) CTTGAATTAA

A card is placed on the plate to shield the right half and prevent exposure to UV light. The organisms are unaffected and free to grow and form a lawn. This is used as a _____.

control

Which of the following would be appropriately sterilized using UV radiation? a) flask of nutrient broth b) nutrient agar plates with lids c) stack of plastic petri dishes, prior to pouring media d) stainless steel surface in biological safety cabinet used for media preparation

d (stainless steel surface in biological safety cabinet used for media preparation)

• Inhibition of growth will be detected when the plate shows a ______ between each half

difference

Specifically, UV light results in the formation of _____, abnormal covalent bonds between adjacent thymine rather than the opposing adenine nucleotides.

dimers

Which structures are less susceptible to UV damage? Fungal spores Endospores Protozoan cysts Vegetative bacterial cells

endospores; protozoan cysts

Physical control methods: • Includes use of h___, c____, i_______, and m_____ r______.

heat; cold; irradiation; mechanical removal

X rays and gamma rays are forms of ____ ____.

ionizing radiation

______ - remove the electrons • Ionize water into highly reactive ____ ____ that damage DNA

ionizing; hydroxyl radicals

In this simulation, a uniform layer of growth, called a _____, will be created on multiple agar plates. • After a bacterial lawn is created, half of the plate will be exposed to UV light for 15sec, 1min, 5min.

lawn

(radiant energy) the shorter wavelengths have ____ _____

more energy

UV and visible light are _______ forms of radiation

non-ionizing

Which of the following infectious agents is least likely to be damaged by UV exposure?

prions

UV light has ______ wavelengths than visible light waves, and its peak energy is at a wavelength of ______.

shorter; 254 nm

Each control method, whether physical or chemical, has a ____ _____ in microbial cells. • The major targets include: 1. Cell wall 2. Cell membrane 3. Synthesis of nucleic acids or proteins 4. Specific metabolic pathways

specific target;

UV radiation is: -Used to _______ some heat-labile solution • Used to ________ hospital operating rooms and food-processing areas • Used to _______ water and milk. ***However, poor penetration (needs direct contact with surface) and is hazardous to human tissue (including eyes) and can result in cancer

sterilize; decontaminate; disinfect

Purpose of lab: to test the effects of UV light exposure for various lengths of ____ to determine how much time is necessary to _____ _____.

time; control growth

Nonionizing radiation between 15 - 400nm is called ________

ultraviolet UV

Write down the different levels of UV wavelengths and their biocidal effectiveness

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