Question 1

Which of the following best describes a chemoheterotroph?

Accepted Answer

An organism that uses organic compounds for both energy and carbon.

Question 2

A microbiologist is culturing a bacterium that grows only at the top of a thioglycollate broth tube. What is the oxygen requirement of this organism?

Accepted Answer

Obligate aerobe

Question 3

Which toxic form of oxygen is most likely to be produced during aerobic respiration and is detoxified by the enzyme superoxide dismutase?

Accepted Answer

Superoxide radical

Question 4

Nitrogen fixation is essential for life on Earth because:

Accepted Answer

It converts nitrogen gas into ammonia, which can be used by living organisms.

Question 5

A bacterium that grows best at pH 9.5 is classified as a(n):

Accepted Answer

Alkalinophile

Question 6

Which of the following statements about osmotic pressure is correct?

Accepted Answer

Osmotic pressure restricts organisms to certain environments based on their ability to tolerate solute concentrations.

Question 7

Which of the following best describes a biofilm?

Accepted Answer

A complex community of microorganisms attached to a surface and embedded in an extracellular matrix.

Question 8

A microbiologist wants to isolate a pure culture from a mixed sample. Which technique should they use?

Accepted Answer

Streak plate method

Question 9

Which type of culture medium would you use to distinguish between bacteria that ferment lactose and those that do not?

Accepted Answer

Differential medium

Question 10

A bacterial culture is stored for decades by removing water under vacuum after freezing. This process is called:

Accepted Answer

Lyophilization

Question 11

If a bacterial population doubles every 30 minutes, how many cells will there be after 2 hours if you start with 1 cell? Use the formula $$N = N_0$ 	imes 2^n$$, where $$n is $$the number of generations.

Accepted Answer

$$N = 1 	imes 2^4$ = 16$$

Question 12

Which phase of the microbial growth curve is characterized by a balance between cell division and cell death?

Accepted Answer

Stationary phase

Question 13

A water sample is filtered and the filter is placed on a nutrient agar plate to count colonies. This method is best described as:

Accepted Answer

Membrane filtration

Question 14

Which of the following is an indirect method for measuring microbial growth?

Accepted Answer

Turbidity measurement using a spectrophotometer

Question 15

A bacterium isolated from deep-sea hydrothermal vents requires high hydrostatic pressure for growth. This organism is best described as a:

Accepted Answer

Barophile

Question 16

Which of the following statements about facultative anaerobes is correct?

Accepted Answer

They can grow with or without oxygen but grow better with oxygen.

Question 17

Which of the following is a growth factor?

Accepted Answer

Amino acid that cannot be synthesized by the organism

Question 18

A microbiologist wants to culture an obligate anaerobe. Which of the following systems would be most appropriate?

Accepted Answer

GasPak anaerobic system

Question 19

Which of the following best explains why most prokaryotes have not been grown in culture medium?

Accepted Answer

They require complex nutrients and growth factors not present in standard media.

Question 20

Which of the following best describes the role of quorum sensing in biofilm formation?

Accepted Answer

It allows bacteria to sense and respond to population density by regulating gene expression.

Microbial Nutrition, Growth, and Culturing: Study Notes

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