Biofilms - Online Tutor, Practice Problems & Exam Prep

Biofilms

In this video, we're going to begin our lesson on Biofilms. 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 extracellular polymeric substance, or in other words, the EPS for short. This extracellular polymeric substance, or the EPS, can be defined as a sticky slime-like matrix that is secreted by cells and helps to support biofilm structure. This extracellular polymeric substance or EPS actually serves to protect cells within the biofilm. It protects cells within the biofilm from harmful conditions such as UV light, chemical toxins, and antibiotics. These biofilm communities of cells really can help to protect cells and can be beneficial for cells. Even resistance genes can actually be transferred between organisms through the DNA that's secreted into this extracellular polymeric substance or EPS.

If we take a look at this image down below, notice that we're focusing on biofilms. Once again, biofilms are going to be communities and groups of cells that live together. 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 extracellular polymeric substance, which is really just this entire gray border and background that we're showing you. Notice zooming in here, we're saying that the extracellular polymeric substance is abbreviated as the EPS, and it is going to be secreted by these cells and helps to create the sticky matrix that ultimately protects cells from harmful conditions such as UV light and toxins. 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.

Over here on the right-hand side, we're also showing you some pretty cool images of multiple bacterial species in a biofilm here and also Staphylococcus aureus bacteria in a biofilm as well. You can see, this grayish-like structure here all the way throughout here extending between these cells is what the extracellular polymeric substance is.

This here concludes our brief introduction to biofilms. 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.

Steps of Biofilm Development

In this video, we're going to begin our lesson on the steps of biofilm development. Biofilm development actually occurs in a series of 4 stages that we have numbered down below 1 through 4. Each of these numbers that you see in the text corresponds with the numbers that you see down below in our image. In the very first step or stage of biofilm development, we have the process of attachment to the surface where the biofilm will begin to develop. This process of attachment is driven by the bacterial cell structures known as fimbriae, which recall from our previous cell videos are these bacterial cell structures that are small and very important for attaching to surfaces. If you take a look at our image down below 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, we have colonization. In this process, those cells that attach are going to begin to multiply and grow as the extracellular polymeric substance or the EPS is going to be produced. If we take a look at our second stage down below, which is again the process of colonization, notice that these bacterial cells that have attached are now beginning to multiply and grow as they contribute to forming the extracellular polymeric substance, which is being represented by this gray background that you see in the back.

Then, in the third step of biofilm development, we have the process of maturation. In this process, the biofilm is going to begin to mature and grow in different ways by having other cells attach. Other cells will attach and also multiply and contribute to the growth of the extracellular polymeric substance or the EPS. If you take a look at our image down below at stage 3, maturation, there are other cells that are going to begin to attach and begin to contribute to the growth of the extracellular polymeric substance. The biofilm is beginning to grow and is really starting to gain more cells to become a community or group of cells.

In the 4th and final step here, we have the process of dispersal. This is when cells can actually detach themselves from the biofilm and the extracellular polymeric substance and can actually leave to help create new biofilms in new locations. If you take a look at this image down below on the right-hand side, notice that this is the process of dispersal. What you can see here is that there are some bacterial cells that are breaking free from the extracellular polymeric 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.

One important thing to note about these biofilms, these communities of cells that are encased in this EPS, is that the cells within the biofilm are actually capable of communicating. They can communicate with each other in a chemical way. This chemical communication is actually described in the process of quorum sensing. We'll be able to talk more about quorum sensing and this chemical communication in our next lesson video. But for now, this here 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.

Biofilms:

• A. Are a random accumulation of bacteria which are not able to communicate with each other.
• B. Are a community of microorganisms protected by a polysaccharide and protein matrix.
• C. Offer no protection against UV light or chemical toxins to microorganisms.
• D. Are large groups of bacteria which are clones of a single parent cell.

Quorum Sensing

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.

What intercellular signaling method do bacterial cells within a biofilm use to understand their own population density?

• A. Quorum sensing.
• B. EPS sensing.
• C. Dispersal sensing.
• D. Quantum sensing.

When will the quorum sensing signaling molecule be in high concentration during biofilm development?

• A. During the attachment phase.
• B. During the quorum phase.
• C. When the bacterial population density is low.
• D. When the bacteria population density is high.