In this video, we're going to continue our introduction to bacterial cell walls by talking about gram-positive and gram-negative bacteria. And so, bacterial cells can be generally categorized based on whether or not they take up what's known as the gram stain. Now, the gram stain is a specific staining procedure that can differentiate bacteria based on differences in their cell walls. Later in our course in a different video, we'll talk a lot more about the differences between gram-positive and gram-negative cell walls. But for now, what you guys should know is that gram-positive bacteria will absorb the Gram stain, whereas gram-negative bacteria do not absorb the gram stain. Let's take a look at our image down below to get a better understanding of this.
What you'll notice is, on the far left over here, what we have are some bacterial cells that are unstained. They are not stained. And after the Gram staining procedure, the purple stain that's used will be absorbed by the gram-positive cells. And so, the gram-positive cells will absorb this purple stain, and so they will become purple themselves. Whereas notice that the gram-negative cells do not absorb the stain, and so they do not turn purple. Once again, the reason why gram-positive absorb the purple stain and gram-negative do not absorb the purple stain has to do with differences in their cell walls. Later in a different video, we'll talk more about the differences in the cell walls of gram-positive and gram-negative bacteria. But for now, this here concludes our brief introduction to gram-positive and gram-negative bacteria. We'll be able to get some practice as we move forward. So, I'll see you all in our next video.