Question 1

Which of the following best describes the role of autoinducers in quorum sensing among Gram-negative bacteria?

Accepted Answer

They are signaling molecules (such as AHL) that accumulate with cell density and trigger gene transcription when a threshold is reached.

Question 2

A patient develops a persistent infection on a catheter. Which microbial property most likely contributes to the difficulty in treating this infection?

Accepted Answer

Biofilm formation, which impairs antibiotic penetration and immune response

Question 3

Which of the following equations best represents the osmotic movement of water across a bacterial cell membrane?

Accepted Answer

$$J = -P (C_{in} - C_{out})$$

Question 4

A bacterium is classified as a halophile. Which environment would it most likely thrive in?

Accepted Answer

A salt pond with NaCl concentration above 3%

Question 5

Which of the following is a direct effect of UV-C light on bacterial DNA?

Accepted Answer

Formation of thymine dimers that disrupt DNA replication

Question 6

Which of the following best explains why buffers are added to bacterial growth media?

Accepted Answer

To maintain equilibrium between H$$^+$$ and OH$$^-$$ concentrations, preventing pH changes that could damage microbial enzymes

Question 7

Which group of bacteria would you expect to find in geothermal hot springs with temperatures above 60°C?

Accepted Answer

Thermophiles

Question 8

A laboratory experiment shows that a bacterial species grows best at pH 4.5. How would you classify this organism?

Accepted Answer

Acidophile

Question 9

Which of the following is NOT a typical consequence of biofilm formation on medical devices?

Accepted Answer

Enhanced immune system clearance

Question 10

Which of the following statements about quorum sensing in Gram-positive and Gram-negative bacteria is correct?

Accepted Answer

Gram-negative bacteria use AHL (N-acyl homoserine lactone) and the LuxIR system for quorum sensing.

Question 11

A bacterial culture is exposed to a hypertonic solution. What is the most likely outcome for the cells?

Accepted Answer

Cells will undergo plasmolysis as water leaves the cytoplasm.

Question 12

Which of the following best describes the cardinal temperatures for bacterial growth?

Accepted Answer

The range of temperatures at which a bacterium can survive, including minimum, optimum, and maximum.

Question 13

Which of the following is a real-world example of a biofilm that can lead to human disease?

Accepted Answer

Dental plaque causing cavities

Question 14

Which of the following best explains why osmotic pressure is important for bacterial survival?

Accepted Answer

It prevents the cytoplasm from shrinking and the cell membrane from separating from the cell wall.

Question 15

Which of the following is a likely outcome if a bacterium is placed in a hypotonic solution?

Accepted Answer

The cell will gain water, but the cell wall prevents bursting.

Question 16

Which of the following is a function of quorum sensing in bacterial communities?

Accepted Answer

Coordinated release of virulence factors

Question 17

Which of the following best describes an osmotic gradient?

Accepted Answer

A difference in solute concentration across a membrane that drives the movement of water by osmosis

Question 18

Which of the following is a characteristic of mesophilic bacteria?

Accepted Answer

They grow best at temperatures between 15°C and 40°C.

Question 19

Which of the following is a reason why biofilms are more resistant to antibiotics than planktonic bacteria?

Accepted Answer

The extracellular matrix impedes antibiotic penetration and provides a protective environment.

Lab 4 Quiz

Guida di studio - Domande di pratica

Study guide - Flashcard