Q: A bacterial culture starts with 100 cells and doubles every 30 minutes. How many cells will there be after 3 hours? Use the formula $$N_f = N_i (2)^g.$$

$$N_f = 100 \times (2)^6$ = 6,400$$

Question 1

A laboratory technician is preparing to culture a clinical specimen suspected of containing an obligate anaerobe. Which of the following methods would best support the growth of this organism?

Accepted Answer

Using a thioglycollate broth to reduce oxygen levels

Question 2

Which of the following best describes the function of agar in microbiological media?

Accepted Answer

Acts as a solidifying agent that is generally not metabolized by microbes

Question 3

A bacterial culture starts with 100 cells and doubles every 30 minutes. How many cells will there be after 3 hours? Use the formula $$N_f = N_i (2)^g.$$

Accepted Answer

$$N_f = 100 	imes (2)^6$ = 6,400$$

Question 4

Which of the following statements about selective and differential media is correct?

Accepted Answer

Selective media favor the growth of certain microbes while inhibiting others; differential media allow visible distinction between species.

Question 5

A patient sample is transported to the laboratory using a specialized medium. What is the primary purpose of transport media?

Accepted Answer

To prevent contamination and maintain viability of the specimen without promoting growth

Question 6

Which of the following growth phases is characterized by a balance between cell division and cell death, often due to nutrient depletion and waste accumulation?

Accepted Answer

Stationary phase

Question 7

A microbiologist observes that a bacterial culture grows optimally at 37$$^	ext{o}C $$and pH 7.0. This organism is most likely classified as a:

Accepted Answer

Mesophile and neutrophile

Question 8

Which of the following best explains why oxygen is toxic to obligate anaerobes?

Accepted Answer

They lack enzymes to detoxify reactive oxygen species such as superoxide radicals and peroxide anions.

Question 9

A food product is preserved by adding high concentrations of salt or sugar. What is the primary effect of this preservation method on microbial cells?

Accepted Answer

It creates a hypertonic environment, causing plasmolysis and inhibiting growth.

Question 10

Which of the following is a trace element required for enzyme function and stabilization of cell components in microbes?

Accepted Answer

Iron (Fe)

Question 11

A scientist wants to culture a bacterium that cannot synthesize its own vitamins. What type of medium should be used?

Accepted Answer

A medium supplemented with the required vitamins

Question 12

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

Accepted Answer

A primitive form of cell division resulting in two genetically identical daughter cells

Question 13

A culture medium contains beef extract, peptone, and agar. This medium is best classified as:

Accepted Answer

Complex

Question 14

A researcher is studying a bacterium that can use CO$$_2 as a $$carbon source and light as an energy source. This organism is classified as a:

Accepted Answer

Photoautotroph

Question 15

Which biosafety level (BSL) requires the use of sealed, negative pressure rooms and suits with independent air supplies for laboratory personnel?

Accepted Answer

BSL-4

Question 16

A bacterial culture is in the log phase of growth. Which of the following best describes what is happening in the culture?

Accepted Answer

Cells are dividing at their maximum rate, resulting in exponential population increase.

Question 17

A scientist observes that a bacterial culture forms endospores during a particular growth phase. Which phase is this most likely to occur?

Accepted Answer

Stationary phase

Question 18

A sample contains 800 bacterial cells after 2 hours. If the population doubles every 30 minutes, how many cells were present at the start? Use $$N_f = N_i (2)^g.$$

Accepted Answer

50 cells

Question 19

Which of the following best describes the role of vitamins in microbial growth?

Accepted Answer

They are organic compounds required in small amounts for enzyme function.

Question 20

A bacterium is classified as a facultative halophile. Which environment would it be able to tolerate?

Accepted Answer

Environments with high or low salt concentrations

Microbial Nutrition and Growth: Requirements, Media, and Growth Dynamics

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