Q: Given a bacterial culture with a generation time of 30 minutes, how many cells will be present after 3 hours if you start with 100 cells? 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 binary fission in bacteria?

Accepted Answer

A single cell divides into two genetically identical daughter cells after chromosome replication and septum formation.

Question 2

A hospital patient develops a persistent infection associated with a catheter. Which microbial growth phenomenon is most likely responsible for the difficulty in treating this infection?

Accepted Answer

Biofilm formation on the catheter surface

Question 3

Given a bacterial culture with a generation time of 30 minutes, how many cells will be present after 3 hours if you start with 100 cells? 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 4

Which growth phase is characterized by a balance between cell division and cell death due to nutrient depletion and waste accumulation?

Accepted Answer

Stationary phase

Question 5

A bacterium that thrives at 70°C and is isolated from a hot spring would be classified as a:

Accepted Answer

Thermophile

Question 6

Which of the following statements about halophiles is correct?

Accepted Answer

They maintain high concentrations of organic materials and ions in their cytoplasm to counteract osmotic stress.

Question 7

Which enzyme is responsible for converting superoxide ions to hydrogen peroxide in aerobic bacteria?

Accepted Answer

Superoxide dismutase

Question 8

A microbe that grows best at pH 3 and is isolated from a volcanic vent is most likely a(n):

Accepted Answer

Acidophile

Question 9

Which of the following media would be most appropriate for isolating a fastidious organism from a clinical sample?

Accepted Answer

Complex (enriched) media

Question 10

Which method would be best for directly counting the number of viable bacteria in a sample?

Accepted Answer

Viable plate count

Question 11

Which of the following statements about autoclaving is correct?

Accepted Answer

It uses steam heat at 121°C and 15 psi to achieve sterilization.

Question 12

Which of the following is a high-level germicide that can sterilize medical equipment by damaging proteins and nucleic acids?

Accepted Answer

Aldehydes (e.g., glutaraldehyde)

Question 13

A bacterium that can grow in the presence or absence of oxygen and can switch between aerobic respiration and fermentation is classified as a:

Accepted Answer

Facultative anaerobe

Question 14

Which of the following best describes a chemoheterotroph?

Accepted Answer

An organism that derives both energy and carbon from organic compounds.

Question 15

Which physical method is most effective for removing prions from surgical instruments?

Accepted Answer

A combination of chemical treatments and increased temperature and pressure during autoclaving

Question 16

Which of the following statements about selective media is correct?

Accepted Answer

It contains ingredients that suppress the growth of some microbes while allowing others to grow.

Question 17

A sample is placed in a spectrophotometer and shows 20% light transmission compared to a control. What does this indicate about the sample?

Accepted Answer

The sample is highly turbid, indicating a high cell density.

Question 18

Which of the following is the best definition of sterilization?

Accepted Answer

The process of destroying all living organisms and viruses, including endospores.

Question 19

Which of the following is a real-world example of a differential medium and its use?

Accepted Answer

Blood agar, which distinguishes bacteria based on their ability to lyse red blood cells.

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