Question

Recall from the text the example of cell communication in Streptococcus pneumoniae: the rate of DNA uptake by pneumococcal cells increases sharply when they are at high density due to changes in gene expression brought about by signaling between cells. If the pneumococcal cells did not express receptor protein, how would the rate of DNA uptake be affected when the cells reach high density?

Please choose the correct answer from the following choices, and then select the submit answer button.


-There would be a larger than normal increase in the rate of DNA uptake.

-There would be a decrease in the rate of DNA uptake.

-There would be no change in the rate of DNA uptake.

-There would be a smaller than normal increase in the rate of DNA uptake.

Answer 1

Without receptor proteins, Streptococcus pneumoniae cells cannot sense high cell density via quorum sensing, leading to a smaller than normal increase in the rate of DNA uptake.

Step-by-step explanation:

If Streptococcus pneumoniae cells did not express receptor protein, the rate of DNA uptake would likely be affected when the cells reach high density. In a normal situation, high cell density leads to an accumulation of autoinducers, which bind to receptors that regulate the transcription of genes, including those responsible for DNA uptake. This process is part of the quorum sensing mechanism that bacteria use to coordinate behavior based on population density. Without functional receptors, the cells would not be able to sense the increased concentration of autoinducers, and thus would not increase the expression of genes involved in DNA uptake. Consequently, there would be a smaller than normal increase in the rate of DNA uptake due to the impaired cell communication.