In this video, we're going to begin our introduction to bacteria. Now before we move on, it's important to emphasize that this video is just an introduction where we will briefly introduce some of the main features of bacteria. However, later in our course, we're going to talk a lot more details about the structures and functions and arrangements of bacteria. And so keep that in mind as we go through this video. Now first, it's important to note that the term bacteria is actually a plural term that's referring to many of the bacterial organisms. However, the singular form of the word is bacterium, which refers to only one single bacterial cell. Now bacteria are going to be organisms in one of the three domains of life, And so recall from our previous lesson videos that the three domains of life are bacteria, archaea, and eukarya. And so bacteria are one of the main domains of life. And it consists of unicellular organisms or organisms that are only made of 1 single cell. And they are also prokaryotic organisms because they lack a nucleus, they have no nucleus. And the bacteria are prokaryotic organisms along with the archaea, which recall are also prokaryotic. Now the bacteria, they can actually vary drastically in their shapes from being spherical in their shape to being rod shaped to even being spiral shaped. And again, we'll get to talk a lot more about the shapes and, the details of these bacteria later in our course. The bacteria can actually range in their length from being somewhere around 0.5 micrometers in length to being up to 10 micrometers in length, at their maximum. They're actually one of the most primitive groups of organisms. The bacteria are believed to be the very first domain to exist, domain of life to exist. So they have been around for 1000000000 of years longer than any other group of organism. The bacteria are major inhabitants of human bodies, and so they're actually found on the surface of our body, on our skins, but they're also found inside of our bodies lining our mucus membranes and things of that nature. And so we'll get to talk a lot more about the bacteria that inhabit our bodies, later in our course. But it's important to note here that these bacteria that inhabit our bodies form what is known as the human microbiota. And so later in our course, we'll get to talk a lot more details about the human microbiota, these bacteria that live on us and in us. Now bacteria, unlike the, eukaryotic organisms, they divide and multiply by a process known as binary fission. And, most of the bacteria are going to have a cell wall that is made of a molecule called peptidoglycan. And so later in our course, this will be one of the major focuses, when we talk about, gram positive and gram negative bacteria. But for now, this is just a brief introduction, and so note that many bacteria have cell walls made of a molecule called peptidoglycan. Now when we get to archaea a little bit later in our course, we'll see that archaea can also have cell walls. However, archaea do not have cell walls made of peptidoglycan. And so peptidoglycan is really a molecule that is unique to the bacterial domain. And again, we'll be able to focus on this detail a lot more later in our course. Now though many bacteria have been studied, it turns out that the vast majority of bacteria, most bacteria remain largely uncharacterized. And so there's still a lot more to know and learn about this domain bacteria. And so if we take a look at our image down below, at this introduction to bacteria, notice that, we're showing you a little snippet of our map of the microbial world from our previous lesson videos. And so notice that, we're focusing in on the prokaryotic groups, specifically the bacteria. And next, we'll be able to talk about the archaea, which, you can see that the the archaea is grayed out here intentionally to show you that that is going to be the next group that we'll talk about. Now over here on the right hand side, you'll see a collage of images showing you many different types of bacteria, such as bacillus anthracis, Vibrio cholerae, streptococcus pyogenes, micrococcus luteus, neisseria gonorrhea, and Escherichia coli. And so, what you'll note is that each of these different types of bacteria, different species and genuses of bacteria, they can have many different shapes and many different structures and features. And so, again, bacteria is a very, very large and diverse group. And, we'll be able to talk a lot more about their structures, their functions, and things of that nature as we move forward. But for now, this here is our, brief introduction to bacteria, 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.