Quorum sensing (QS) in bacteria regulates their gene expression in a population-density dependent manner, which controls population behaviors. Once the population reach a high density and so do the QS molecules, the expression of many genes in bacteria are triggered. Do bacteria still keep on producing QS signals once their population is high? How do they regulate QS production?
It depends on bacterial species. In general, there's a positive response loop. When the sensor regulator senses QS molecules, it up regulates the genes for the synthesis of QS molecules. So the producing of QS signals will go up for a while. However, most bacteria have negative regulatory mechanisms to shut down quorum sensing. The activation of QS pathway may lead to the expression of negative regulators that reduces the production of QS molecules.
Several types of quorum sensing have been discovered to date. For example: there are species specific autoinducers (QS molecules) known as acyl-homoserine lactones which have been discovered in many bacteria. There is also interspecies quorum sensing through the autoinducer-2 molecule which has been found in several species as well. There are also other quorum sensing molecules that are peptides.
In Vibrios for example, the quorum sensing master regulator (LuxR) which is activated by the presence of a high concentration of AI-2 molecules (QS molecules), regulates many genes (activates or represses). Interestingly, LuxR also increases transcription of the gene that codes for the enzyme that catalyzes the formation of AI-2. This may imply that at high cell density when there are more and more QS molecules around, even more is being produced.
To get a more detailed answer about specific quorum sensing systems I would look at some of the literature. Here's a good paper to give you some idea
http://everettsd.schoolwires.net/cms/lib07/WA01920133/Centricity/Domain/1010/Quorum%20Sensing%20-%20Bassler%20Article.pdf
I hope this helps.
-Mez
- Badges
- Science topic
- Similar topics
- Biological Science
- Microbiology
- Microorganisms
- Bacteria