Oxygen Requirements for Microbial Growth

in this video, we're going to begin our lesson on oxygen requirements for microbial growth. And so it turns out that all organisms that utilize chemical energy require what's known as a final electron except er for their electron transport chain. Now, later in our course, in a different video, we'll talk a lot more about these final electronic sectors and electron transport chain. But for now, here in this video, you can just imagine that the final electronic sector and electron transport chain are important for generating energy for the cell. Now in many microbes, the final electron except er in this electron transport chain, is going to be oxygen gas, or 02. And so organisms that utilize oxygen gas as the final electronic except er are referred to as Arabs. And so Arabs are really just microbes that require oxygen gas to act as the final electronic sector in the electron transport chain. And therefore, these Arabs are going to require oxygen to be abundant in order for them to grow. And so Arabs only grow where oxygen is abundant and we call these um areas these environments that have lots of oxygen aerobic environments. And so Arabs require oxygen for growth and so therefore they grow only in aerobic environments where there's lots of oxygen. Now, on the other hand, anna robes are microbes that grow where little to no oxygen is present and when little to no oxygen is present, we refer to these as anaerobic environments. And so if we take a look at our image down below, notice on the left hand side over here, we're focusing in on aerobic environments. And so in Arabic environment, there is plenty of oxygen. And Arabs are capable of surviving in Arabic environments. And so here we're showing you an arab because notice he's saying, I can't live without you speaking to the oxygen gas. And so Arabs require oxygen to be present. And an example of that is Mycobacterium tuberculosis, which is a bacterium that causes tuberculosis, which is a long condition now. On the right hand side over here, what we're focusing on is the anaerobic environment and the anaerobic environment is the opposite of the Arabic environment. Anaerobic environments do not have a lot of oxygen and so Arabs are capable of surviving and anaerobic environments. And so over here, what we have is an arab and notice this one has a completely different opinion of oxygen and saying, no, thank you, I do not need oxygen to grow. And so an example of this uh arrow and a robe. I'm sorry, is going to be bacteria bacteria Otis for jealous, which is a bacterium that survives in the gastrointestinal tract of humans. And so this year concludes our brief introduction to oxygen requirements for microbial growth and how Arabs grow in Arabic environments with lots of oxygen and anna robes grow in anaerobic environments with little to no oxygen. And so we'll be able to learn more about the oxygen requirements for microbial growth as we move forward in our lessons. So I'll see you all in our next video.

in this video, we're going to begin our lesson on oxygen requirement classes of microbes. And so microbes can really be classified into five groups based on their requirement for oxygen gas. Or go to And so notice down below in this table, we're showing you the oxygen requirement classes of microbes. And so they're organized into these five groups that we have numbered one through five. Now, one thing that's very important to note here is that each of these five groups has these test tubes and these test tubes that you see here are really special test tubes, because they allow for really, really high concentrations of oxygen towards the top of the test tube, represented by these light blue backgrounds. And then as you start to go towards the bottom of the test tube, you start to get lower oxygen concentrations. And so at the very bottom of each of these test tubes is the lowest oxygen concentrations. And this is something that's very important to keep in mind as we move forward throughout the rest of this video. And so the very first group that we have over here on the far left are the obligate Arabs. And as their name implies, these are going to be uh aerobic organisms or organisms that are obligated to aerobic environments or environments that have high oxygen concentrations. And so notice that all of these brown speckles that you see throughout here represent microbial growth, and there's only microbial growth here in the region of the test tube that has the highest oxygen concentration. And so obligate Arabs cannot live without oxygen. And so notice here we have an obligation. Arab saying, I can't live without you to the oxygen gas because they require they absolutely require oxygen gas and cannot live without the oxygen gas. Now, the next group that we have here are the faculty native anna robes, and as their name implies, faculty of anna robes can survive in both aerobic and anaerobic environments. And so what you'll notice is that there are brown speckles throughout the entire test tube. However, what you should also notice is that there's a lot more brown speckles towards the top of the test tube than there are towards the bottom of the test tube. And this is because faculty tive anna robes, although they can grow in both the presence and absence of oxygen, they actually grow a lot better in the presence of oxygen gas. And so that's why there's a lot more um microbes in the aerobic region of the test tube, in the region has higher oxygen, and there's less faculty of anna robes in the region to have lower oxygen. And so notice that this microbe where there's no oxygen is saying this is okay, I guess. And really, this is his number two options to have no oxygen present. But when they're an aerobic environments where oxygen is present, notice the microbe is saying, this is amazing and the presence of oxygen is going to be, it's number one option to be able to grow best. And so there is uh microbial growth throughout the entire test tube. However, there's going to be a lot more towards the regions that have higher oxygen. And the reason for this is because oxygen allows for the generation of more ATP more energy and more energy means more growth and that's why they're able to grow more and better in aerobic environments. Now, the next group that we have over here, the third group are going to be the micro Arrow files. And so micro is a route that we know means small. And so these Arabs micro Arrow files. They do not need much oxygen at all. In fact, too much oxygen is actually toxic to these micro Arrow files. And so they do require oxygen. However, they require small amounts of oxygen because if it's too high then they are, it's going to be toxic to them. And so notice that they grow right here in this very specific region where there is a small amount of oxygen, but notice that they're not at the very, very top where there's the most amount of oxygen. And they also do not grow where there's no oxygen. And so they do require oxygen, but they only require a small amount of oxygen gas. Now, the next group that we have over here are going to be the obligate anna robes. An obligate anaerobic are practically the opposite of obligate Arabs. And that's because obligate anaerobic can only survive where there is no oxygen. And oxygen is pretty much toxic to these obligatory anna robes. And so notice that this obligate anaerobic saying get away from me and he's got his protective shield and sword because the oxygen is toxic to these obligations and arose. And so they cannot grow in the presence of oxygen. They require uh anaerobic environments, environments that have no oxygen in order to grow. And so that's why we see all of the microbial growth is towards the very bottom of the tube. And there's absolutely no growth whatsoever in any of the regions that have oxygen because oxygen is toxic to the obligate anaerobic. And then the 5th and final group that we have over here are the arrow tolerant and the robes and the arrow tolerant and robes are really going to grow equally in oxygen. And uh areas that have no oxygen. So they grow equally an aerobic and anaerobic environments. And so notice that the microbial growth is evenly distributed. They do not grow better in one or the other. They grow equally in both. And so here, what we're saying is that these arrow tolerant. Arabs and Arabs are tolerant to both oxygen and uh tolerant to regions that have no oxygen as well. So they grow in the presence or the absence of oxygen equally. And so notice that it's a, I love them both, and it doesn't really matter to these microbes whether there's oxygen or no oxygen present, They grow equally in both. And so really, these are the five classes of oxygen requirements for microbes. 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 reactive oxygen species. And so Arabs, which recall from our previous lesson videos are microbes that require oxygen gas, tend to generate toxic derivatives of oxygen called reactive oxygen species. And so reactive oxygen species are commonly abbreviated as just R. O. S. For short. And so reactive oxygen species. Or roos are highly reactive oxygen molecules that can cause damage to the cell. And so reactive oxygen species. Or roos present a problem for Arabs. And so examples of reactive oxygen species, or roos include super oxide, which is 02 minus as well as hydrogen peroxide, Which is H202. And so super oxide and hydrogen peroxide are capable of causing damage to the cell. Now, uh these Arabs need to have a way to be able to manage these reactive oxygen species. And so all Arabs produce enzymes that protect the self from these reactive oxygen species or roos. And so here what we're showing our three enzymes that these Arabs can use to protect themselves from the reactive the reactive oxygen species. And so the first enzyme that we have here is super oxide dis mutates and super oxide. This mutation is abbreviated as S. O. D. And this is an enzyme that will convert to super oxide molecules two of these reactive oxygen species, super oxide molecules into oxygen gas and hydrogen peroxide. And so if we take a look at our image down below here, which will notice is reactive oxygen species, or R. O. S. Include oxygen 02 minus, which is super oxide as well as hydrogen peroxide or H And once again, these can cause damage to the cell. And so these three enzymes help to protect the Arabs from these reactive oxygen species. And so the first enzymes super oxide dis mutates, converts to super oxide molecules or two oh two minus molecules, and it converts them in this reaction with hydrogen ions into hydrogen peroxide and oxygen gas. Then the next enzyme that we have here is going to be catalysts and cattle is is an enzyme that converts to hydrogen peroxide molecules into oxygen gas and two molecules of water. And so notice that the enzyme catalysts converts to hydrogen peroxide molecules into two water molecules and oxygen gas. And so water and oxygen gas is nontoxic to Arabs. And so basically by using these enzymes, uh these Arabs are able to convert toxic reactive oxygen species into non toxic components. And so sometimes they need to work together to help convert these toxic components, these toxic reactive oxygen species into non toxic molecules of water and oxygen gas. And then the third and final enzyme that we're going to talk about here is peroxide days, which is going to be an enzyme that converts hydrogen peroxide into water. And so if we take a look at this image down below the peroxide is, enzyme is able to convert hydrogen peroxide H uh, and two hydrogen ions into two water molecules, again converting toxic reactive oxygen species into non toxic components such as water and oxygen. And so this year concludes our brief lesson on reactive oxygen species, these toxic components that tend to be generated by Arabs and also the enzymes that Arabs used to protect themselves from the their own reactive oxygen species that they generate. And so we'll be able to get some practice applying these concepts as we move forward in our course. So I'll see you all in our next video.