In this video, we're going to begin our lesson on oxygen requirement classes of microbes. Microbes can be classified into 5 groups based on their requirement for oxygen or O2. Notice in the table below, we're showing you the oxygen requirement classes of microbes organized into these 5 groups, numbered 1 through 5. It's important to note that each of these 5 groups has test tubes.
These test tubes are special because they allow for very high concentrations of oxygen towards the top of the test tube, represented by light blue backgrounds. As you move towards the bottom of the test tube, the oxygen concentrations decrease, reaching the lowest levels at the very bottom. This is crucial to keep in mind as we continue with this video. The first group on the far left are the obligate aerobes.
Obligate aerobes, as the name implies, are aerobic organisms or those that require environments with high oxygen concentrations. The brown speckles you see represent microbial growth, which occurs only in the region of the test tube with the highest oxygen concentration. Obligate aerobes cannot live without oxygen. Notice the obligate arrow saying, "I can't live without you," to the oxygen gas because they absolutely require oxygen gas and cannot survive without it. The next group is the facultative anaerobes.
Facultative anaerobes, as their name suggests, can survive in both aerobic and anaerobic environments. There are brown speckles throughout the entire test tube, with a higher concentration towards the top where there is more oxygen, demonstrating that facultative anaerobes grow better in the presence of oxygen gas. This is important because oxygen allows for the generation of more ATP, meaning more energy and better growth. The next group, the third, are the microaerophiles.
Microaerophiles require small amounts of oxygen; too much oxygen is toxic to them. They grow in a specific region where there's a small amount of oxygen, not at the very top where there is the most oxygen, and also not at the bottom where there is no oxygen. The next group are the obligate anaerobes, practically the opposite of obligate aerobes. Obligate anaerobes can only survive where there is no oxygen, which is toxic to them. Notice this obligate anaerobe using a protective shield and sword against oxygen, indicative of the fact that oxygen is highly toxic to these organisms. Growth is seen only at the very bottom of the tube where there is no oxygen.
The fifth and final group are the aerotolerant anaerobes, which grow equally in oxygen and areas that have no oxygen. They do not grow better in one environment over the other; they are equally tolerant to both. Notice it's saying, "I love them both," indicating it doesn't matter to these microbes whether there's oxygen or not. They grow equally in both. These are the 5 classes of oxygen requirements for microbes, and we'll get some practice applying these concepts as we move forward.
So I'll see you all in our next video.