Question 1

Which of the following best describes antimicrobial resistance in microorganisms?

Accepted Answer

The acquired ability of a microorganism to resist the effects of a chemotherapeutic agent to which it is normally susceptible.

Question 2

Which of the following is NOT a typical mechanism by which bacteria develop antimicrobial resistance?

Accepted Answer

Increased permeability to antibiotics

Question 3

Tolerance in microorganisms is often associated with which of the following?

Accepted Answer

The physiological state of the cell and its potential similarity to resistance mechanisms.

Question 4

Which two-component system is responsible for the regulation of porin synthesis in bacteria?

Accepted Answer

EnvZ/OmpR

Question 5

In a two-component regulatory system, what is the typical sequence of signal transduction?

Accepted Answer

Membrane-integrated sensor kinase autophosphorylates, then transfers the phosphoryl group to a cytoplasmic response regulator.

Question 6

Which of the following equations best represents the phosphorylation reaction in a two-component system?

Accepted Answer

$$\mathrm{HK} + \mathrm{ATP} \rightarrow \mathrm{HK{-}P} + \mathrm{ADP}$$

Question 7

Which of the following is a correct example of a two-component system involved in bacterial virulence?

Accepted Answer

PhoQ/PhoP system in Salmonella

Question 8

Chemotaxis in bacteria is best described as:

Accepted Answer

The movement of bacteria in response to chemical gradients, either toward attractants or away from repellents.

Question 9

Which protein governs the direction of flagellar rotation in E. coli during chemotaxis?

Accepted Answer

CheY

Question 10

What is the effect of repellents on the bacterial flagellar motor?

Accepted Answer

Repellents cause the flagellar motor to rotate clockwise, leading to tumbling.

Question 11

Which of the following statements about quorum sensing is TRUE?

Accepted Answer

Quorum sensing allows cells to communicate and coordinate gene expression based on population density.

Question 12

In Pseudomonas aeruginosa, which quorum-sensing system is required for virulence gene activation under certain growth conditions?

Accepted Answer

Rhl system

Question 13

Which of the following best explains why Vibrio cholerae uses quorum sensing to repress biofilm formation and virulence gene expression?

Accepted Answer

To prevent unnecessary energy expenditure and avoid detection by the host immune system when cell density is high.

Question 14

Which of the following is a real-world example of quorum sensing controlling gene expression?

Accepted Answer

Regulation of bioluminescence in Vibrio fischeri

Question 15

Which equation best represents the threshold effect in quorum sensing, where gene expression is induced only when signaling molecule concentration exceeds a critical value?

Accepted Answer

$$[S] \u003e [S]_c \Rightarrow 	ext{Gene Expression Activated}$$

Question 16

Which of the following is a plausible consequence of bacterial adaptation or desensitization to a chemoeffector?

Accepted Answer

A higher concentration of the chemoeffector is required to elicit a response.

Question 17

Which of the following is TRUE regarding the photoresponse in bacteria?

Accepted Answer

Photoresponse depends on light wavelength, with cells attracted to certain wavelengths and repelled by others.

Question 18

Which of the following best describes the role of two-component systems in environmental response?

Accepted Answer

They allow bacteria to detect environmental signals and regulate gene expression accordingly.

Question 19

Which of the following is a multi-step process involving both chemotaxis and quorum sensing in a pathogenic bacterium?

Accepted Answer

A bacterium moves toward a nutrient-rich area (chemotaxis), then activates virulence genes once a high cell density is reached (quorum sensing).

Microbial Regulatory Systems: Resistance, Adaptation, and Communication (lecture 7)

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