Q: A bacterial species has a generation time of 30 minutes. If you start with 100 cells, how many cells will there be after 3 hours of optimal growth? Use the formula $$N = N_0$ \times 2^n$$, where $$n is $$the number of generations.

$$N = 100 \times 2^6$ = 6400$$ cells

Question 1

Which of the following best describes the process of biofilm formation in a clinical setting, such as on a catheter?

Accepted Answer

Free-floating (planktonic) bacteria adhere to the surface, produce a sticky polysaccharide matrix, and allow other microbes to join, forming a collaborative community.

Question 2

A bacterial species has a generation time of 30 minutes. If you start with 100 cells, how many cells will there be after 3 hours of optimal growth? Use the formula $$N = N_0$ 	imes 2^n$$, where $$n is $$the number of generations.

Accepted Answer

$$N = 100 	imes 2^6$ = 6400$$ cells

Question 3

Which type of microbe would most likely thrive in a soda lake with high salt and high pH?

Accepted Answer

A halo-alkaliphile

Question 4

Why are endospores particularly difficult to eliminate using boiling water as a decontamination method?

Accepted Answer

Endospores can survive hours of boiling due to their resistant structure, making boiling ineffective for sterilization.

Question 5

Which laboratory method allows for the differentiation between living and dead cells using fluorescent tags?

Accepted Answer

Flow cytometry

Question 6

A patient is infected with Mycobacterium tuberculosis. Which property of this microbe makes it especially challenging to disinfect surfaces contaminated with it?

Accepted Answer

Its cell wall is rich in waxy mycolic acids, making it resistant to many disinfectants.

Question 7

Which of the following is a correct application of selective and differential media in a clinical laboratory?

Accepted Answer

Using media that inhibits the growth of non-pathogenic microbes while allowing pathogens to grow and be distinguished by color changes.

Question 8

Which of the following statements about halophiles is TRUE?

Accepted Answer

Halophiles thrive in environments with high salt concentrations and avoid plasmolysis by storing high concentrations of organic materials or ions.

Question 9

Which physical method of decontamination is most suitable for sterilizing heat-sensitive medical equipment such as pacemakers?

Accepted Answer

Ethylene oxide gas sterilization

Question 10

A microbiologist wants to maintain a bacterial culture in the log phase for industrial production. Which device is most appropriate for this purpose?

Accepted Answer

Chemostat

Question 11

Which of the following chemical agents is classified as a high-level germicide and is effective against endospores?

Accepted Answer

Peracetic acid

Question 12

Which equation correctly represents the action of catalase in detoxifying reactive oxygen species?

Accepted Answer

$$2H_2O_2 \rightarrow 2H_2O + O_2$

Question 13

Which of the following best explains why prions are difficult to eliminate from surgical instruments?

Accepted Answer

Prions withstand autoclaving and chemical sterilization, requiring a combination of chemical treatments and increased temperature and pressure.

Question 14

Which of the following is a correct distinction between disinfectants and antiseptics?

Accepted Answer

Disinfectants are used on inanimate objects, while antiseptics are applied to living tissue.

Question 15

A sample of bacteria is diluted and plated using the streak plate technique. What is the primary purpose of this method?

Accepted Answer

To isolate individual colonies from a mixed culture for further study.

Question 16

Which of the following statements about microbial nutrient requirements is correct?

Accepted Answer

Macronutrients such as carbon are needed in large amounts, while micronutrients like iron are required in very small amounts.

Question 17

Which of the following is a correct example of a fastidious organism?

Accepted Answer

A bacterium that requires multiple growth factors, such as vitamins and amino acids, to be supplied in its medium.

Question 18

Which of the following physical methods is most effective for sterilizing large volumes of air in a hospital setting?

Accepted Answer

High-efficiency particulate air (HEPA) filtration

Question 19

A microbiologist uses a spectrophotometer to measure the turbidity of a liquid culture. What is being assessed by this method?

Accepted Answer

The cloudiness of the culture, which correlates with cell density.

Chapter 7: Microbial Growth and Decontamination – Study Notes

Study Guide - Practice Questions

Study Guide - Flashcards