Question

some microbes use qs signaling pathways to trigger the expression of virulence genes. the expression of these genes enhances the virulence, or harmfulness, of the microbial infection. which of the following represents the best method to decrease the virulence of a microbe capable of qs? choose 1 answer: a develop a drug that increases the cell density of the microbial infection. b develop a drug that increases the binding of qs signaling molecules to their receptors. c develop a drug that decreases the cell density needed to express virulence genes. d develop a drug that decreases the cell density of the microbial infection.

Explanation:

To decrease the virulence of a microbe using Quorum Sensing (QS), we need to disrupt the QS pathway that triggers virulence gene expression. QS is often dependent on cell density (more cells mean more signaling molecules to trigger virulence).

• Option A: Increasing cell density would likely increase QS - mediated virulence gene expression, so this is incorrect.
• Option B: Increasing the binding of QS signaling molecules to their receptors would enhance the QS pathway and thus increase virulence, so this is incorrect.
• Option C: Decreasing the cell density needed to express virulence genes would make it easier for the microbe to reach the density required for virulence gene expression, increasing virulence, so this is incorrect.
• Option D: Decreasing the cell density of the microbial infection would reduce the number of signaling molecules (since QS is density - dependent). With fewer signaling molecules, the QS pathway is less likely to be activated to trigger virulence gene expression, thus decreasing virulence.

Answer:

D. Develop a drug that decreases the cell density of the microbial infection.