Q: A bacterial culture starts with 100 cells and has a generation time of 30 minutes. How many cells will there be after 8 hours of growth in ideal conditions? Use the formula: $$N = N_0$ \times 2^n$$, where $$n = \frac{t}{g}.$$

$$N = 100 \times 2$$^{16}$$ = 6,553,600$$

Question 1

Which of the following best describes a chemoheterotroph?

Accepted Answer

An organism that uses chemical compounds as an energy source and organic compounds as a carbon source.

Question 2

A bacterium is found growing only at the top of a thioglycollate broth tube. Which term best describes its oxygen requirement?

Accepted Answer

Obligate aerobe

Question 3

Which enzyme is responsible for converting superoxide radicals ($$O_2$$^-$$) into hydrogen peroxide (H_2O_2$) and oxygen (O_2$)?

2O_2^- + 2H$$^+ \rightarrow H_2O_2 + $$O_2$$

Accepted Answer

Superoxide dismutase

Question 4

A bacterial culture starts with 100 cells and has a generation time of 30 minutes. How many cells will there be after 8 hours of growth in ideal conditions?

Use the formula: $$N = N_0$ 	imes 2^n$$, where $$n = \frac{t}{g}.$$

Accepted Answer

$$N = 100 	imes 2$$^{16}$$ = 6,553,600$$

Question 5

Which of the following best explains why obligate anaerobes are killed by oxygen?

Accepted Answer

They lack enzymes to detoxify reactive oxygen species.

Question 6

Which of the following is a growth factor required by some bacteria for cell membrane synthesis?

Accepted Answer

Cholesterol

Question 7

A bacterium that grows optimally at pH 3 and can produce acid as a metabolic byproduct is best classified as a:

Accepted Answer

Acidophile

Question 8

Which of the following statements about biofilm formation is correct?

Accepted Answer

Quorum sensing triggers changes in gene expression during biofilm maturation.

Question 9

Which of the following best describes the adaptation of extreme halophiles to high-salt environments?

Accepted Answer

They maintain a high internal solute concentration to prevent plasmolysis.

Question 10

Which of the following is NOT a stage in the typical bacterial growth curve?

Accepted Answer

Sporulation phase

Question 11

A bacterium that can grow in the presence or absence of oxygen, but grows better with oxygen, is classified as a:

Accepted Answer

Facultative anaerobe

Question 12

Which of the following is a real-world example of a disease caused by endospore-forming bacteria?

Accepted Answer

Anthrax

Question 13

Which of the following best describes the process of binary fission in bacteria?

Accepted Answer

The cell elongates, replicates its DNA, forms a cross-wall, and separates into two identical cells.

Question 14

Which of the following best explains why Listeria monocytogenes is a concern in refrigerated foods?

Accepted Answer

It is a psychrotroph that can grow at low temperatures.

Question 15

Which of the following equations correctly calculates the number of generations ($$n) $$that have occurred between two population measurements $$P_1$$ and $$P_2$$?

$$P_1 = $$initial population, $$P_2 = $$final population

Accepted Answer

$$n = \frac{\log P_2$ - \log P_1$}{\log 2}$$

Question 16

Which of the following is a trace element required by microorganisms in very small amounts?

Accepted Answer

Iron

Question 17

A bacterium that grows best at 70°C is classified as a:

Accepted Answer

Thermophile

Question 18

Which of the following best describes the function of quorum sensing in biofilms?

Accepted Answer

It allows bacteria to sense and respond to population density.

Question 19

Which of the following is a correct statement about persister cells?

Accepted Answer

They can survive antibiotic treatment and become active when conditions improve.

Question 20

Which of the following best describes the effect of a hypertonic environment on a bacterial cell?

Accepted Answer

The cell undergoes plasmolysis as water leaves the cell.

Microbial Growth and Nutrition: Factors, Mechanisms, and Population Dynamics

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