Nester's Microbiology: A Human Perspective
9th Edition
ISBN: 9781259709999
Author: Denise G. Anderson Lecturer, Sarah Salm, Deborah Allen
Publisher: McGraw-Hill Education
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Chapter 5, Problem 2CT
This diagram shows the filter paper method used to evaluate the inhibitory effect of chemical agents, heavy metals, and antibiotics on bacterial growth. A culture of a test bacterium is spread uniformly over the surface of an agar plate. Small filter paper discs containing the material to be tested are then placed on the surface of the medium. A disc that has been soaked in sterile distilled water is sometimes added as a control. After incubation, a lawn (film of growth) will cover the plate, but a clear zone will surround those discs that contain an inhibitory compound. The size of the zone reflects several factors, one of which is the effectiveness of the inhibitory agent. What are two other factors that might affect the size of the zone of inhibition? What is the purpose of the control disc? If a clear area were apparent around the control disc, how would you interpret the observation?
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This diagram shows the filter paper method used to evaluate the inhibitory effect of chemical agents, heavy metals, and antibiotics on bacterial growth. A culture of a test bacterium is spread uniformly over the surface of an agar plate. Small filter paper discs containing the material to be tested are then placed on the surface of the medium. A disc that has been soaked in sterile distilled water is sometimes added as a control. After incubation, a lawn (film of growth) will cover the plate, but a clear zone will surround those discs that contain an inhibitory compound. The size of the zone reflects several factors, one of which is the effectiveness of the inhibitory agent. What are two other factors that might affect the size of the zone of inhibition? What is the purpose of the control disc? If a clear area were apparent around the control disc, how would you interpret the observation?
A pure culture was inoculated onto a Mueller-Hinton agar plate. The Kirby-Bauer procedure was performed. One of the drugs tested showed a large zone of inhibition but also had small colonies growing within this zone. Further testing showed that these colonies were not the results of contamination. Why would these colonies be present within this zone of inhibition?
A lab technician is working with a bacterium in pure culture (in 5 ml of liquid media in a test tube). The bacterium is a mesophile that can infect humans. Which of the following is NOT true (with regards to temperature conditions for this bacterial culture)?
Lowering the temperature to -10 deg C for at least an hour will likely kill all the bacteria.
Placing the tube at 37 deg C will likely facilitate rapid growth of the bacteria.
Raising the temperature to 90 deg C for at least an hour will likely kill all the bacteria.
Placing the tube at 4 deg C will likely slow or halt growth of the bacteria.
Chapter 5 Solutions
Nester's Microbiology: A Human Perspective
Ch. 5 - How is preservation different from pasteurization?Ch. 5 -
2. What is the most chemically resistant...Ch. 5 - Explain why it takes longer to kill a population...Ch. 5 - What is the primary reason that wine is...Ch. 5 -
5. What is the primary reason that milk is...Ch. 5 - When canning, why are low-acid foods processed at...Ch. 5 - How are heat-sensitive liquids sterilized?Ch. 5 -
8. How does microwaving a food product kill...Ch. 5 -
9. How is an iodophore different from a tincture...Ch. 5 - Name two products commonly sterilized using...
Ch. 5 - Unlike a disinfectant, an antiseptic a) sanitizes...Ch. 5 - The D value is defined as the time it takes to...Ch. 5 - Prob. 3MCCh. 5 - Prob. 4MCCh. 5 - Which concentration of alcohol is the most...Ch. 5 - All of the following could be used to sterilize an...Ch. 5 - All of the following are routinely used to...Ch. 5 - Aseptically boxed juices and cream containers are...Ch. 5 - Commercial canning processes are designed to...Ch. 5 -
10. Which of the following is false?
a) A...Ch. 5 - An agriculture extension agent is preparing...Ch. 5 - As a microbiologist representing a food...Ch. 5 - This graph shows the time it takes to kill...Ch. 5 -
2. This diagram shows the filter paper method...
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