Quorum sensing is something that bacterial cells can use to communicate. The signals that the bacteria produce are N-acyl-homoserine lactones or AHLs. These signals can be received by the bacterial species or different bacterial species. There are two primary genes involved in quorum sensing. There is the I gene which codes for AHL synthase and the R gene which is a transcriptional regulator. AHL synthase, which the I gene codes for, is responsible for producing the AHL signal that other bacterial cells will be able to receive. The AHL binds to a receptor on a neighboring cell and a transcriptional response is activated, this is where the R gene begins to function. The R gene transcribes new DNA in response to the signal being received. For example the bacteria C. violaceum produces a purple pigmented antibiotic violacein, C. violaceum only produces this antibiotic after it has received a signal from a neighboring cell telling it to do so. Quorum sensing is vital for bacteria living in the environment to communicate with neighboring cells.
Comments
suggestion
One suggestion I have has to do with your first sentence where you say "Quorum sensing is something that bacterial cells can use to communicate." Using the word "something" is vague and I would be more specific about what this "something" means.
Suggestion
"There is the I gene which codes for AHL synthase and the R gene which is a transcriptional regulator. AHL synthase, which the I gene codes for is responsible for producing the AHL signal..."
I think here that repeating the same information nearly verbatim a second time, especially in the very next sentence, is unnecessary. You can just say "AHL synthase is responsible for ..." and go from there.
comment
One suggestion would be to pay careful attention to word choice "this is where the R gene begins to function", instead of "where", perhaps you meant "when"