In this video, we're going to begin our lesson on a process known as quorum sensing. Recall from our previous lesson videos, we mentioned that biofilms are groups or communities of cells living together, encased in an extracellular polymeric substance, or an EPS. We know that these biofilms contain many different cell types, and these different cell types can communicate with one another chemically. Quorum sensing is the name of one of the processes by which these cells communicate.
Quorum sensing is a bacterial process of detecting their own population density or even detecting the presence of other cells. It allows for the detection of extracellular signaling molecules that are going to be released or secreted by other cells in the extracellular polymeric substance. The signaling molecule concentration actually increases with an increase in cell density. By detecting these chemical concentrations, they are also able to sense the cell densities either of their own population or other cell populations.
If we look at the image below, we can get a better understanding of quorum sensing. Notice on the left-hand side, we're showing some bacterial cells in a relatively low density. There are not many bacterial cells, so the bacterial cell concentration is quite low, leading to a lower signaling molecule concentration. These pink circles represent the signaling molecules, which are being produced and released by the bacteria. The fewer the bacteria, the fewer signaling molecules will be released, leading to a low concentration of this particular signaling molecule. This low concentration is a way for the cells to detect a low density of the cells, potentially initiating these cells to begin replicating and create more cells.
On the right-hand side, there are a lot more bacterial cells, leading to a higher bacterial cell concentration and, consequently, a higher signaling molecule concentration. Because these bacterial cells can detect this signaling molecule, they can ascertain the density of their own population and the density of other cell populations as well. Quorum sensing is an amazing ability that bacterial cells within a biofilm can have. This concludes our brief lesson on quorum sensing, and we'll be able to get some practice applying these concepts as we move forward. I'll see you all in our next video.
