Question 1

Which of the following best describes a psychrotroph?

Accepted Answer

A microorganism that grows between 0°C and 30°C, with an optimum around 25°C

Question 2

A bacterium is found growing in a hot spring at 90°C. Which temperature classification does it most likely belong to?

Accepted Answer

Hyperthermophile

Question 3

Which of the following equations correctly represents the reaction catalyzed by superoxide dismutase?

Accepted Answer

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

Question 4

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

Accepted Answer

They lack enzymes to detoxify harmful oxygen forms such as superoxide radicals

Question 5

A bacterium that can grow in the presence or absence of oxygen, using fermentation or anaerobic respiration when oxygen is not available, is classified as:

Accepted Answer

Facultative anaerobe

Question 6

Which of the following is a chemical requirement for microbial growth that is a component of DNA, RNA, and ATP, and is found in phospholipids?

Accepted Answer

Phosphorus

Question 7

What is the effect of placing a bacterial cell in a hypertonic solution?

Accepted Answer

The cell will undergo plasmolysis due to water leaving the cell

Question 8

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

Accepted Answer

Stationary phase

Question 9

A laboratory is working with a pathogen that requires sealed, negative pressure rooms and HEPA filtration. Which biosafety level is required?

Accepted Answer

BSL-4

Question 10

Which of the following statements about biofilms is FALSE?

Accepted Answer

Biofilms are rarely involved in human infections

Question 11

Which of the following best describes the role of trace elements in microbial growth?

Accepted Answer

They act as enzyme cofactors and are required in small amounts

Question 12

A microorganism that grows best at pH 3 is classified as a(n):

Accepted Answer

Acidophile

Question 13

Which of the following is the correct formula to calculate the total number of cells after n generations, starting from a single cell?

Accepted Answer

$$2^n$$

Question 14

Which of the following is NOT a function of biofilms?

Accepted Answer

Increasing susceptibility to antibiotics

Question 15

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

Accepted Answer

The rate of cell division equals the rate of cell death

Question 16

Which of the following is a toxic form of oxygen that is the most reactive free radical?

Accepted Answer

Hydroxyl radical ($$OH^\cdot)$$

Question 17

A bacterium that requires high salt concentrations for growth is called a(n):

Accepted Answer

Obligate halophile

Question 18

Which of the following is a correct description of a microaerophile?

Accepted Answer

Requires oxygen at concentrations lower than atmospheric levels

Question 19

Which of the following is NOT a chemical requirement for microbial growth?

Accepted Answer

Temperature

Question 20

Which of the following statements about binary fission is TRUE?

Accepted Answer

It doubles the number of cells each generation

Microbial Growth: Physical and Chemical Requirements, Oxygen Effects, Biofilms, and Growth Dynamics

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