in this video we're going to begin our lesson on biofilms. And so recall from our previous lesson videos that biofilms can be defined as groups or communities of cells that are encased in a slime like layer anchored to a surface. Now this slime like layer is actually referred to as the extra cellular pollen merrick substance. Or in other words the E. P. S. For short. And so this extra cellular problematic substance or the E. P. S. For short can be defined as a sticky slime like matrix that is secreted by cells and helps to support biofilm structure. Now this extra cellular polymorphic substance or E. P. S. Actually serves to protect cells within the biofilm and so it protects cells within the biofilm from harmful conditions such as UV. Light chemical toxins and antibiotics. And so these biofilm communities of cells really can help to protect cells and can be beneficial for cells. And even resistance genes can actually be transferred between organisms through the D. N. A. That's actually secreted into this extra cellular polly merrick substance or E. P. S. And so if we take a look at this image down below notice that we're focusing in on biofilms and once again biofilms are going to be communities and groups of cells that live together. And so notice that here in this image on the left we're showing you a biofilm communities of cells, bacteria and archaea that live together encased in this extra cellular pollen merrick substance which is really just this entire gray border and background that we're showing you. And so notice zooming in here were saying that the extra cellular problematic substance is abbreviated as the E. P. S. And it is going to be secreted by these cells and helps to create the sticky matrix that ultimately protect cells from harmful conditions such as UV light and toxins. And so notice that we're showing you the toxins and UV light somewhat bouncing off to portray the fact that they are protected from those agents. Now, over here on the right hand side, we're also sending you some pretty cool images of multiple bacterial species in a biofilm here and also staphylococcus aureus bacteria in a biofilm as well. And so you can see uh this grayish like structure uh here. All the way through out here, extending between these cells is what the extra cellular pol american substance is. And so this year concludes our brief introduction to biofilms. And as we move forward, we'll be able to learn more about biofilms and apply these concepts as well. So I'll see you all in our next video.

in this video, we're going to begin our lesson on the steps of biofilm development. And so biofilm development actually occurs in a series of four stages that we have numbered down below one through four. And each of these numbers that you see in the text correspond with the numbers that you see down below in our image. And so in the very first step or stage of biofilm development, What we have is the process of attachment, which, as its name implies, is when the cells are actually going to attach themselves to the surface where the biofilm will begin to develop. And this process of attachment is driven by the bacterial cell structures known as for embryo, which recall from our previous sell videos are these bacterial cell structures that are small and very important for attaching to surfaces. And if you take a look at our image down below, over here, on the left hand side, we have a visualization of this first stage of attachment where cells such as bacterial cells will attach themselves to the surface, where the biofilm will begin to develop in the second stage of biofilm development. What we have is colonization. And in this process those cells that attached are going to begin to multiply and grow as the extra cellular pollen, merrick substance or the E. P. S. Is going to be produced. And so if we take a look at our second stage down below, which is again the process of colonization uh noticed that these bacterial cells that have attached are now beginning to multiply and grow as they contribute to forming the extra cellular pol american substance which is this gray which is uh being represented by this gray background that you see in the back. Uh Then in the third step of biofilm development. What we have is the process of maturation. And in this process uh the biofilm is going to begin to mature and grow in different ways by having other cells attach and so other cells will attach and also multiply and contribute to the growth of the extra cellular pol american substance or the E. P. S. And so if you take a look at our image down below at stage three maturation, uh there are other cells that are going to begin to attach and begin to contribute to the growth of the extra cellular pol american substance. So the biofilm is beginning to grow and is really starting to gain more cells to become a community or group of cells. And then in the fourth and final step here, what we have is the process of dispersal. And this is when cells can actually detach themselves from the biofilm and the extra cellular polymorphic substance and can actually leave to help create new biofilms and new locations. And so if you take a look at this image down below, over here on the right hand side, notice that this is the process of dispersal. When you can see here is that there are some bacterial cells that are breaking free from the extra cellular polly merrick substance, breaking free from the biofilm and so they can travel to new locations and try to attach themselves and begin the process of creating a biofilm in a completely different location. Now, one thing that's also important to note about these biofilms, these communities of cells that are encased in this E. P. S. Um is that the cells that are within the biofilm are actually capable of communicating and so they can communicate with each other in a chemical way. And uh this chemical communication is actually uh described in the process of quorum sensing. And so we'll be able to talk more about quorum sensing and this chemical communication in our next lesson video. But for now, this year concludes our brief lesson on the steps of biofilm development, and we'll be able to get some practice applying these concepts as we move forward. So I'll see you all in our next video.

in this video, we're going to begin our lesson on a process known as quorum sensing. And so recall from our previous lesson videos, we said that biofilms are groups or communities of cells that live together encased in an extra cellular pollen eric substance or E. P. S. And so we know that these biofilms actually contain many different cell types and these different cell types can actually have the ability to communicate with one another in a chemical way. And so a process known as quorum sensing is the name of one of the processes by which these cells can actually communicate with one another. And so quorum sensing is a bacterial process of detecting their own population density or even detecting the presence of other cells. And so uh quorum sensing allows for the detection of extra cellular signaling molecules that are going to be released or secreted by other cells in the extra cellular pollen merrick substance. And the signaling molecule concentration is actually going to increase Okay with an increase in the cell density. And so the higher, by detecting these chemical concentrations, they're also able to detect the cell densities either of their own population or of the population of other cells. And so if we take a look at our image down below, we can get a better understanding of quorum sensing. And so notice over here on the left hand side that we're showing you some bacterial cells. Uh and these bacterial cells notice that are in a relatively low density. There are not that many bacterial cells over here. So the bacterial cell concentration is quite low over here and having a lower bacterial cell concentration is going to lead to having a lower signaling molecule concentration, or the signal molecule concentration also being low. And so notice that here in pink, these pink circles actually represent the signaling molecules. And so the signaling molecules are being produced and released by these bacteria. And so uh the lower the less bacteria there are, the less signaling molecules will be released. And so having a low concentration of this particular signaling molecule is a way for the cells to detect um a low density of the cells. And so having a low concentration of the signaling molecule could initiate these cells to begin replicating and start to create more cells. And so that's what we see over here on the right hand side is a lot more bacterial cells notice that there are a lot more bacterial cells and with higher bacterial cell concentration that is going to lead to a higher signaling molecule concentration. And so the signal molecule concentration is much higher with the higher self density. And so because these bacterial cells have the ability to detect this signaling molecule, uh they have the ability to detect the density of their own population and the density of other cell populations as well. And so quorum sensing is an amazing ability that these bacterial cells can have. And once again, quorum sensing is something that can allow bacterial cells within a biofilm to communicate with each other. And so this year concludes our brief lesson on quorum sensing, and we'll be able to get some practice applying these concepts as we move forward. So I'll see you all in our next video.