Q: Which equation is used to calculate the total number of cells after n generations?

$$N_{total} = N_{initial} \times 2^n$$

Question 1

Which of the following best describes a chemoheterotroph?

Accepted Answer

Uses organic compounds for both energy and carbon.

Question 2

A bacterial culture is placed in a medium with a pH of 5.6. What is the most likely outcome?

Accepted Answer

Fungal colonies will grow better than bacterial colonies.

Question 3

Which phase of the microbial growth curve is characterized by cells adjusting to their environment and not actively dividing?

Accepted Answer

Lag phase

Question 4

During which phase of the microbial growth curve are bacteria most susceptible to antibiotics?

Accepted Answer

Logarithmic (exponential) phase

Question 5

A culture starts with 10 cells and has a generation time of 30 minutes. How many cells will there be after 3 hours?

Accepted Answer

640

Question 6

Which equation is used to calculate the total number of cells after n generations?

Accepted Answer

$$N_{total} = N_{initial} 	imes 2^n$$

Question 7

Which of the following is NOT a toxic form of oxygen?

Accepted Answer

Hydroxyl ion

Question 8

Why are obligate anaerobes killed by oxygen?

Accepted Answer

They lack enzymes to detoxify oxygen radicals.

Question 9

Which enzyme catalyzes the decomposition of hydrogen peroxide into water and oxygen?

Accepted Answer

Catalase

Question 10

What is nitrogen fixation?

Accepted Answer

Reduction of nitrogen gas ($$N_2) to $$ammonia ($$NH_4$$^+$$) by certain bacteria.

Question 11

Which of the following best describes a mesophile?

Accepted Answer

Requires temperatures ranging from 20°C to 40°C.

Question 12

Which method is used to estimate microbial population size by measuring turbidity?

Accepted Answer

Spectrophotometry

Question 13

Which of the following is a real-world example of a biofilm?

Accepted Answer

Microbes colonizing a contact lens case

Question 14

Why are biofilm-associated infections difficult to treat?

Accepted Answer

Biofilm cells are protected by an extracellular matrix and have altered gene expression.

Question 15

Which of the following best describes a facultative anaerobe?

Accepted Answer

Can live with or without oxygen.

Question 16

Which physical requirement for microbial growth is most likely to affect the tertiary structure of proteins?

Accepted Answer

Temperature

Question 17

A bacterial cell is placed in a hypertonic solution. What is the most likely outcome?

Accepted Answer

The cell will shrink due to water loss.

Question 18

Which of the following is a growth factor?

Accepted Answer

Vitamin B12

Question 19

Which microbial association is characterized by members living in close nutritional or physical contact and becoming interdependent?

Accepted Answer

Symbiotic

Question 20

A patient with a heart valve infection is found to have a persistent biofilm. Which property of biofilms most likely contributes to the persistence of this infection?

Accepted Answer

Biofilm cells are protected by an extracellular matrix and are released continuously.

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