Question 1

Which of the following best describes a biofilm?

Accepted Answer

A collection of microbes living on a surface in a complex community, often formed through quorum sensing.

Question 2

Which group of organisms uses carbon dioxide as a carbon source and light as an energy source?

Accepted Answer

Photoautotrophs

Question 3

Obligate anaerobes are killed by oxygen because:

Accepted Answer

Toxic forms of oxygen cause irreparable damage to cellular components.

Question 4

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

Accepted Answer

Dihydrogen monoxide

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

Obligate halophiles require high osmotic pressure for growth.

Question 7

Which of the following best explains why nitrogen fixation is essential to life on Earth?

Accepted Answer

It converts atmospheric nitrogen into forms usable for amino acids and nucleotides.

Question 8

A culture medium that contains substances that inhibit the growth of some bacteria while allowing others to grow is called:

Accepted Answer

Selective medium

Question 9

Which of the following is a direct method for measuring microbial growth that does NOT require incubation?

Accepted Answer

Microscopic count using a cell counter

Question 10

A bacterial culture has a generation time of 30 minutes. If you start with 1 cell, how many cells will there be after 3 hours of logarithmic growth? Use the formula $$N = N_0$ 	imes 2^n$$, where $$n is $$the number of generations.

Accepted Answer

$$N = 1 	imes 2^6$ = 64$$

Question 11

Which of the following best describes the stationary phase of a bacterial growth curve?

Accepted Answer

The number of live cells remains constant as cell division equals cell death.

Question 12

Why are biofilms of particular concern in medical settings such as on cardiac devices or respiratory equipment?

Accepted Answer

Microorganisms in biofilms are often more resistant to antibiotics and disinfectants.

Question 13

Which of the following is a reason why clinical laboratory scientists keep many different kinds of culture media on hand?

Accepted Answer

Different microorganisms have unique nutritional and environmental requirements.

Question 14

A sample is taken from a 2-week-old bacterial culture in the death phase and transferred to fresh media. What is the most likely outcome?

Accepted Answer

Growth will occur because some cells remain viable even in the death phase.

Question 15

Which of the following best describes a chemoheterotroph?

Accepted Answer

Uses organic compounds as both energy and carbon sources.

Question 16

Which of the following is a multi-step method for obtaining a pure culture from a mixed sample?

Accepted Answer

Streak plate method followed by incubation and colony selection.

Question 17

Which of the following statements about defined (synthetic) media is correct?

Accepted Answer

The exact chemical composition is known.

Question 18

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

Accepted Answer

Facultative anaerobe

Question 19

Which of the following is a physical requirement for microbial growth that affects the three-dimensional structure of proteins?

Accepted Answer

Temperature

Question 20

Which of the following methods is used to estimate the number of viable microorganisms in a sample by serial dilution and plating?

Accepted Answer

Viable plate count

Microbial Nutrition and Growth: Study Notes for Microbiology Students

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