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 statements about acidophiles is correct?

Accepted Answer

They grow in acidic environments

Question 4

What happens to a bacterial cell placed in a hypertonic solution?

Accepted Answer

The cell will undergo plasmolysis as water leaves the cell

Question 5

Which of the following is a chemical requirement for microbial growth?

Accepted Answer

Sulfur

Question 6

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 7

Which enzyme catalyzes the reaction $$-O_2$^- + O_2$^- + 2H^+ \rightarrow H_2O_2 + O_2$ to detoxify superoxide radicals?

Accepted Answer

Superoxide dismutase

Question 8

Which of the following best explains why biofilms are difficult to eradicate in medical settings?

Accepted Answer

Biofilms are 1000x more resistant to microbicides than planktonic cells

Question 9

Which phase of the bacterial growth curve is characterized by rapid cell division and exponential increase in cell number?

Accepted Answer

Log phase

Question 10

A culture starts with 1 cell. After 10 generations, how many cells will there be? Use the formula $$N = 2$$^{n}$$, where N$ is the number of cells and n$ is the number of generations.

Accepted Answer

$$N = 1024$$

Question 11

Which of the following is NOT a function of trace elements in microbial growth?

Accepted Answer

Serving as a structural backbone of organic molecules

Question 12

Which oxygen classification describes bacteria that require oxygen at concentrations lower than atmospheric levels (5-10% O$$_2) $$and elevated CO$$_2$$?

Accepted Answer

Microaerophile

Question 13

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

Accepted Answer

The rate of cell division equals the rate of cell death

Question 14

Which of the following is a correct description of facultative halophiles?

Accepted Answer

They can tolerate high osmotic pressure but do not require it

Question 15

Which of the following is a toxic form of oxygen that is the active component of hydrogen peroxide?

Accepted Answer

Peroxide anion

Question 16

A patient with a catheter develops a persistent infection. Which microbial property is most likely responsible for the persistence of this infection?

Accepted Answer

The bacteria form biofilms on the catheter surface

Question 17

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

Accepted Answer

It is a component of DNA, RNA, and ATP

Question 18

Which biosafety level (BSL) requires sealed, negative pressure rooms and HEPA-filtered exhaust air?

Accepted Answer

BSL-4

Question 19

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

Accepted Answer

They lack enzymes such as superoxide dismutase and catalase to detoxify reactive oxygen species

Question 20

Which of the following equations correctly represents the catalase reaction for detoxifying hydrogen peroxide?

Accepted Answer

$$2H_2O_2 \rightarrow 2H_2O + O_2$

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

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