in this video, we're going to begin our lesson on endo spores. And so recall from way back in our previous lesson videos that a scientist of the name, john Tyndall discovered a heat resistant form of bacterial cells which were later termed endo spores. And so these endo spores can be defined as a dormant cell that is only produced by some bacteria and are highly resistant to damaging conditions. And so because these endo spores are resistant to damaging conditions, this means that they're able to survive and damaging conditions where most normal cells would not be able to survive and because these endo sports are dormant. What that means is that they are going to have lowered activity and they are not going to be able to perform the same functions as normal cells would. But once again, they are highly resistant to damaging conditions, such as extreme amounts of heat. They are also highly resistant to toxic chemicals and they are resistant to nutrient depletion. And so these endo spores are able to survive a lot of conditions where once again, most normal cells would not be able to survive. Now. What's also really important to note about these endo scores is that endo scores are not a form of replication and so it does not allow a cell to replicate and reproduce. Instead, endospore formation is actually going to start and end with a single cell. And so it does not form more cells and so it's not a form of replication. Instead, endospore formation is going to be a form of survival. And so all it does is it allows cells to survive these damaging conditions where they might not otherwise be able to survive. Now, it's also important to note that a vegetative cell is the scientific way to refer to a normal cell that is going to be replicating and is not dormant. And so we'll be able to see how vegetative cells can actually form endo spores when nutrients are depleted down below in this image. And so notice on the left hand side over here, what we're showing you is a vegetative cell which is basically the normal bacterial cell under normal conditions. And so notice that there are nutrients available by the plus nutrients. It's just saying that nutrients are available and so you can see these little hexagons that represent glucose being available in the environment. However, notice that when there are no nutrients available in the environment, the vegetative cell can undergo a process called sport regulation which will talk more about later. And that is the process that forms an endospore. And so when there are no nutrients again, when nutrients are depleted, the cell can begin to form an endospore. And so here what we have is the endospore and the end of spore is still alive. However, it is a dormant cell and so it's going to have lowered activity and it's not gonna be able to perform the same functions as the vegetative cell. However, it is able to survive the conditions when there's no nutrients and so once nutrients become available once again then the endo's four can undergo a process called germination, which we will talk more about later in our course as well. And that is the process by which an endo's for reverts back into a vegetative cell. And so the vegetative cell is going to be the cell that is going to be able to be performing more of the normal functions. And so uh what's important to note here is that endo sports are usually only produced by gram positive cells such as for example bacillus and Clostridium are two examples of bacteria that are gram positive and produce endo spores. And so one way to help you remember that it's gram positive cells that typically perform or typically form endo scores is that you can think of. Endo spores are dormant like winter clothes in the summer and the back of your closet. And so what you can think is when the temperature is positive Celsius. So when the temperature is warm, like in the summer, your winter clothes are going to be in a dormant state in the back and you're not going to be using them very often. And so by thinking of the positive Celsius here that can help remind you of gram positive cells are the ones that form end of sports. And so that's just a little memory tool that can be helpful for you. And so this year concludes our brief introduction to kendo spores and we'll be able to apply the concepts that we've learned here 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 endo's for structure. And so an endospore consists of somewhere between five and 6 layers surrounding the innermost region of the endospore called the core. And so the more layers and endospore has the more protected the endospore is from the environment. And once again recall from our previous lesson videos that endo spores are a form of survival and so they need to be protected and need to be resistant to several damaging conditions. And they do that by having several layers. And so let's take a look at this image down below, at a typical endospore structure. And so what you see over here on the left is representing the entire endospore and notice that it comes in several different layers at the very very center. What we have is the core of the endospore. And this is where the chromosomal DNA will be stored. And then as you go from the inside to the outside, you have the inner membrane, which is the light blue that's going around the core right here. And then what you have in orange is the germ cell wall. And so there's a cell wall that's going to be going around it like. So then what you have is the cortex is the next layer here. That would be this layer here in light blue. Going all the way around. Uh Then what we have is the outer membrane. So that would be this membrane in green here, going all the way around. And then what we have is what's known as the coat, which is just another layer here in purple. And then blast. But not least what we have on the final layer out here is what's known as the exhaust story. Um and the exhaust story um is not always found in all endo spores. And so that's why we say 5-6 layers here. And so the idea here is the more layers there are around the end of score, the more protected it is and the more resistant it is too damaging conditions. And so speculation is actually the name of the process of endo's for formation. And so endo spores form by the process known as speculation. And so speculation is the process of endospore formation from a vegetative cell. When the environment is unfavorable, basically in damaging conditions. The vegetative cell will perform speculation to form an endo sport and so we'll be able to talk more about this process of speculation as we move forward in our course. But for now this year concludes our brief introduction to endospore structure 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