Q: Which of the following equations best represents the synthesis of c-di-GMP from GTP?

$$2\ \mathrm{GTP} \rightarrow \mathrm{c\text{-}di\text{-}GMP} + 2\ \mathrm{PP_i}$$

Question 1

Which of the following best describes a biofilm?

Accepted Answer

A group of bacterial cells adhered to a surface and enclosed in a self-produced matrix, typically composed of polysaccharides.

Question 2

Why do bacteria form biofilms? Select the BEST answer.

Accepted Answer

To resist physical forces, remain in a favorable niche, and live in close association with other cells.

Question 3

Which of the following is NOT a function of the extracellular matrix in a biofilm?

Accepted Answer

Facilitating the direct uptake of oxygen from the environment.

Question 4

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

Accepted Answer

Biofilms protect bacteria from immune responses and antibiotic penetration.

Question 5

Which signaling molecule is central to the regulation of biofilm formation in many bacteria?

Accepted Answer

Cyclic di-Guanosine monophosphate (c-di-GMP)

Question 6

Quorum sensing in bacteria involves which of the following processes?

Accepted Answer

The production and detection of signaling molecules to coordinate gene expression based on population density.

Question 7

Which of the following is a correct sequence of events in biofilm formation?

Accepted Answer

Attachment → Colonization → Development → Active Dispersal

Question 8

Which of the following best explains why biofilms are more tolerant to antibiotics than planktonic (free-living) bacteria?

Accepted Answer

The extracellular matrix limits antibiotic penetration and cells in biofilms may be metabolically dormant.

Question 9

Which of the following is an example of a disease or condition associated with biofilm formation in humans?

Accepted Answer

Cystic fibrosis lung infections

Question 10

A researcher is studying a bacterial strain that produces a signaling molecule which diffuses freely across the cell envelope and binds to an activator protein, triggering gene transcription. This is an example of:

Accepted Answer

Quorum sensing

Question 11

Which of the following equations best represents the synthesis of c-di-GMP from GTP?

Accepted Answer

$$2\ \mathrm{GTP} ightarrow \mathrm{c	ext{-}di	ext{-}GMP} + 2\ \mathrm{PP_i}$$

Question 12

Which of the following is NOT a mechanism by which bacteria can resist the effects of antibiotics?

Accepted Answer

Increasing the permeability of the cell membrane to antibiotics.

Question 13

A hospital isolate of Staphylococcus aureus is found to be resistant to methicillin due to the presence of the mecA gene. This is an example of which resistance mechanism?

Accepted Answer

Metabolic bypass of the antibiotic target

Question 14

Which of the following best describes the function of the AcrAB-TolC efflux pump in Escherichia coli?

Accepted Answer

It exports a variety of antibiotics out of the cell, contributing to multidrug resistance.

Question 15

Which of the following statements about persister cells is TRUE?

Accepted Answer

Persister cells are dormant variants of regular cells that are transiently tolerant to antibiotics.

Question 16

A patient with cystic fibrosis is infected with Pseudomonas aeruginosa. The infection is difficult to treat because the bacteria form biofilms. Which TWO features of biofilms contribute most to this difficulty? (Select the best answer.)

Accepted Answer

Biofilms limit antibiotic penetration and contain dormant cells less susceptible to antibiotics.

Question 17

Which of the following is a real-world consequence of biofilm formation in industrial settings?

Accepted Answer

Biofilms can slow the flow of liquids and accelerate corrosion of pipes.

Question 18

Which of the following best explains why quorum sensing is important for the regulation of virulence factors in pathogenic bacteria?

Accepted Answer

It ensures that virulence factors are only produced when a sufficient population density is reached, maximizing their effectiveness.

Question 19

Which of the following is a correct statement about the role of c-di-GMP in bacterial cells?

Accepted Answer

High levels of c-di-GMP promote biofilm formation and reduce motility.

Question 20

A bacterial population is exposed to an antibiotic. After treatment, a small fraction of cells survive and regrow when the antibiotic is removed. These surviving cells are most likely:

Accepted Answer

Persister cells that were dormant during antibiotic exposure.

Surfaces, Biofilms, and Microbial Communication

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