Posted: November 29th, 2022

BIOL 2420 Microbiology for the Health Sciences

BIOL 2420 Microbiology for the Health Sciences Name: ___________________________
Week 12 DUE Sunday, Nov. 13, 2022/ ____ 5 pts

Microbial Control – Questions and Reflections

The following questions below are to be answered for each lab and used as a guideline to study for the practical.

1. Read the Lab Introductions from the Introduction PPT for each exercise.
2. Watch Recorded Video(s)
a. Kirby-Bauer Assay Video: : https://www.youtube.com/watch?v=Np87w5kCL-4
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1. Exp. 7-3 Antimicrobial Susceptibility (Kirby-Bauer Method)
A disk diffusion test used to measure effectiveness (sensitive, intermediate, or resistant) of antimicrobial agents (any natural or synthetic substance that kills microorganisms). Example: Penicillin antibiotic is produced by the mold Penicillium notatum.

a. What is the absence of microbial growth around a disc called?
b. What does “a synergistic effect of two antibiotics” mean?
c. What are two explanations for the presence of colonies in the clear areas (zone of inhibition)?
d. Name two variables of the test that are standardized to ensure comparable results between labs around the world.
e. DRAW the results for both antibiotic plates, the gram positive and gram negative, for comparison.
f. Which antibiotic was most effective for controlling gram negative organism?
g. Which antibiotic was most effective for controlling for gram positive organism?
h. Name three organisms (genus/species) that produce antibiotics and the antibiotic each makes.

2. Disinfectants and other antimicrobials – Handout on Microbugz
The “Use Dilution Method” is a standard procedure used to measure a disinfectant’s effectiveness against microorganisms and establish appropriate dilutions for disinfectants. Concentrations for use are determined by growth comparison with a control sample.

a. DRAW the disinfectant and essential oil result plates for gram positive and gram negative organisms?
b. Which antimicrobial was the most effective for the gram positive organisms?
c. Which antimicrobial was the most effective for the gram negative organisms?
d. What concentration of bleach is commonly used in the laboratory? (you may use outside sources)
e. What concentration isopropyl alcohol is considered most effective against microorganisms and commonly used in the laboratory? (you may use outside sources)

3. Exp. 10-5 Ultraviolet Radiation Damage and Repair

a. How specific damage does ultraviolet light cause in DNA?
b. From the experimental results in the PPT, after approximately what exposure time can an endospore-forming organism no longer repair its DNA?
c. From the experimental results in the PPT, after approximately what exposure time can a non endospore-forming organism no longer repair its DNA?

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