Question 1

Which of the following best describes the sequence of events in biofilm formation as depicted in the provided images?

Accepted Answer

Planktonic cell → Attached cell → Microcolony → Biofilm → Detached cell

Question 2

Which cellular structure is primarily responsible for the initial movement of bacteria toward a surface during biofilm formation?

Accepted Answer

Flagella

Question 3

During the transition from planktonic to biofilm-associated cells, which gene expression change is commonly observed in *Pseudomonas aeruginosa*?

Accepted Answer

Decreased flagellin synthesis and increased alginate production

Question 4

Which of the following best explains why biofilm-associated bacteria are more resistant to antibiotics than planktonic cells?

Accepted Answer

The exopolysaccharide matrix impedes antibiotic penetration and cells may grow more slowly.

Question 5

Which signaling molecule is most commonly associated with quorum sensing in single-species biofilms?

Accepted Answer

Acyl-homoserine lactones (acyl-HSLs)

Question 6

A marine bacterium is exposed to a nutrient-poor environment containing both chitin and glass surfaces. According to the study material, where is the bacterium most likely to attach?

Accepted Answer

It will preferentially attach to the chitin surface.

Question 7

Which of the following is a direct consequence of increased horizontal gene transfer within biofilms?

Accepted Answer

Rapid emergence of new pathogens with antibiotic resistance

Question 8

In the context of biofilm development, what is the primary role of exopolysaccharides?

Accepted Answer

They stabilize the three-dimensional structure of the biofilm.

Question 9

Which experimental method is commonly used to identify bacterial mutants defective in biofilm formation?

Accepted Answer

Staining biofilm-associated cells with crystal violet after removing planktonic cells

Question 10

Which of the following best describes the spatial distribution of bacteria within a multispecies biofilm?

Accepted Answer

Bacteria are organized based on their ability to survive in specific microenvironments and symbiotic relationships.

Question 11

Which of the following equations best represents the relationship between the rate of antibiotic penetration ($$P) $$and the thickness of the biofilm ($$d$$), assuming simple diffusion?

Accepted Answer

$$P = \frac{k}{d}$$

Question 12

A mutant *Pseudomonas aeruginosa* strain lacks the ability to produce acyl-HSLs. What is the most likely phenotype regarding its biofilm structure?

Accepted Answer

It forms biofilms with closely packed cells that are easily disrupted.

Question 13

Which of the following is a plausible adaptive advantage for bacteria to produce exopolysaccharide lyase under starvation conditions in a biofilm?

Accepted Answer

To degrade the biofilm matrix for nutrient acquisition and facilitate escape.

Question 14

Which of the following best explains why intercellular signaling is more effective in biofilms than in planktonic cultures?

Accepted Answer

Biofilms provide a diffusion-limited environment, concentrating signaling molecules.

Question 15

Which of the following is NOT a function of intercellular communication in multispecies biofilms?

Accepted Answer

Ensuring all species are evenly distributed throughout the biofilm

Question 16

Which of the following statements about the detachment phase in the biofilm life cycle is correct?

Accepted Answer

Detachment allows bacteria to colonize new surfaces when conditions become unfavorable.

Question 17

Which of the following best describes the role of type IV pili in biofilm formation?

Accepted Answer

They facilitate movement along surfaces and microcolony formation.

Question 18

In a dental plaque biofilm, what is the primary factor determining the spatial distribution of different bacterial species?

Accepted Answer

Specific coaggregation interactions between oral bacteria

Question 19

Which of the following is a likely outcome if a bacterium in a biofilm fails to repress flagellum synthesis?

Accepted Answer

The bacterium may destabilize the biofilm and detach prematurely.

Question 20

Which of the following best describes the relationship between nutrient availability and surface attachment in marine bacteria?

Accepted Answer

In nutrient-poor environments, bacteria preferentially attach to nutritive surfaces like chitin.

Biofilm Formation and Microbial Communities: Structure, Function, and Genetic Regulation

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