Nitrogen Fixation

nitrogen is an essential nutrient toe living organisms, and the reason for this is it's a required element in both nuclear acids and proteins. So pretty much the basics need this stuff. And for us animals, we just have to eat something that has nitrogen in it, done deal and a story plants don't have. It is easy, though. They have to obtain their nitrogen through some more complex means. Now. Nitrogen actually cycles through ecosystems in a very creatively termed chemical cycle called the nitrogen cycle, and in this process, nitrogen is actually converted through a variety of chemical forms. The most abundant form that plants will see nitrogen in is and two in the atmosphere, this atmospheric, gaseous nitrogen. It's actually almost 80% of the atmosphere. It's technically, it's about 78%. We'll just call it 80. Keep it nice and even or nice round numbers. Um, thing is, plants can't absorb this nitrogen sucks for them. They can't absorb this gashes, and two, they actually are going to rely on this process that bacteria and archaea will carry out called nitrogen fixation, which is the conversion of that gashes end to into this usable NH three ammonia form of nitrogen. Now plants are actually going to absorb mostly ammonium right, which is the protein ated form of this. Um, you know, ammonia is a weak base, so you know, after it's chemically converted, it's gonna pick up a proton turned into ammonium, most likely, and they also will absorb these nitrates, which will come as a product of various downstream reactions after the bacteria and archaea convert the a gaseous nitrogen into ammonia. So these were the two main forms absorbed by plants. But it's important to note that not every plant is going to rely on this process. In fact, carnivorous plants, for example, use carnivorous to supplement their nitrogen intake. Yeah, I mean, if you ever wondered, why do plants which make their own food right plants make their own sugar? Why would they need to eat these other organisms? Well, it's actually it's not to gain, uh, nutrition Thio. You know, uh, burn in the sense that sugar is used. It's actually to obtain more nitrogen. That's why they eat animals, right? Animals that are made up of meat and therefore have bunch of nitrogen in them. Now, some plants like EP if ICTs actually don't contact soil it all. They have toe live on other plants, and they actually absorb all their water and nutrients from the air, the rain and just like the debris that surround them. So it's important to remember that, you know, life has so much variety. There's always going to be exceptions. But nitrogen fixation in a large part is what plants are going thio rely on in order to obtain their nitrogen. You can see this nice chart here shows how nitrogen cycles through ecosystems in the course of the nitrogen cycle, and you might notice that decompose er's right D composers actually also contribute to night to the ammonium. In fact, de composers will also provide some sources of nitrogen to plants. Talk a little bit more about that later. Now this process. This nitrogen fixation is super energy intensive, and that's why so few species exist that can carry this out. It's really just confined to you. You know, some species of bacteria and archaea. It za really energy intensive process. It's mainly facilitated by this multi enzyme complex called nitrogenous. Another creative name for you in this complex is going to reduce caches nitrogen into ammonia, so it basically facilitates nitrogen fixation. Now, as I said, this process is extremely energy intensive. And in fact, to convert one just one molecule. I don't mean one more one molecule of and two into two molecules of NH three. Um, and that that's just for chemical balancing their right. We have to nitrogen. So we're gonna need two of these pneumonias to have our, uh, chemistry balance out. We have our balanced equation under here. If you're curious. Don't worry about memorizing it, though. Um so to convert just that one molecule of gaseous nitrogen into two molecules of pneumonia requires eight high energy electrons and a whopping 16 ATP you can see behind my head there. So this is a massively energy intensive process, especially when you consider that these guys, they're not just converting one molecule. They're going to be converting tons and tons of molecules into ammonia, making it usable to plants. So a lot of energy required. Fortunately, they can lean on plants a little bit to get some of that energy. We'll talk about that when we flip the page

While some nitrous flying bacteria are content to live in the soil and pass off the fruits of their labor to their fellow plants, some want to take this step further, and we'll actually perform nitrogen fixation inside plant roots. Mostly this occurs in plants of the lagoon Family Lagoon's air flowering plants with the Latin name FIBA, and they carry these rise obeah bacteria in what are called na jewels. In their roots. Now rise obeah are gram negative soil bacteria that perform nitrogen fixation, and they do so in the roots of these legumes. Technically, that makes them end of fights or organisms that live inside other plants. Usually they are fungi or bacteria. Nah, jewels are swollen nodes or lumps in the roots where these bacteria have infected the plants. And make no mistake, even though this relationship is beneficial for both both organisms. This is technically a bacterial infection in the plant, and that's why the swelling occurs. I mean, if you've ever seen a swollen lump in a tree stump or something like that, that's also a site of infection. That's in part how plants will respond to infections. And that is why these swollen lumps look like infections because they are infections. But it's not, you know, unwanted infection. In fact, plants are inviting these bacteria in by releasing these chemicals into the soil called flavonoids. And these actually signal the rise obeah who in turn released their own signal, which are called nod factors. And these nod factors will actually come into contact with the root hairs. So I'm gonna jump out of the image here and just draw right here. So let's pretend here we have Benny Bacteria. Or maybe Rebecca rise obeah. Whatever you wanna think of it, the groups flavonoids will be released by the root hair, and they're gonna make their way to Rebecca. Rise obeah over here, and in turn, she's going to release her, not factors. And that is going to stimulate the root hair and cause a morphological change that will actually allow the bacteria to enter into the cortex the inner part of the plant, through what's called an infection thread. So, basically, Rebecca rise obeah here. I'm just gonna put our our for now she is going thio, uh, take advantage of that morphological change. Enter the root hair, go through the root hair cell and make her way into the cortex. So this is supposed to be cortex sell here. And this, of course, a root hair. So once inside the actual plant cortex, these rise obeah are going to set up shop. You can see an actual image of what this looks like here. All of these dark, uh, lumps are bacteria living in the plant cell, and they're going to get along swimmingly. Actually, they have a mutual ist IC relationship because the plant provides carbohydrates and protection to the bacteria right, and the bacteria is going to provide usable nitrogen. And remember earlier I said that the energy demands of performing nitrogen fixation are very great. But these plants right in this mutual ist IC relationship there helping the bacteria out with those energy demands. They're saying, Hey, look, you're giving us nitrogen. Here's some carbohydrate that you'll be able to convert into a teepee, and then you can use that 80 p to make the nitrogen usable for us. So it's like, you know, you scratch my back, I'll scratch yours Now. In addition, plants will also, uh, are These lagoons will also produce this molecule called leg hemoglobin and hopefully you can pick out that word. Hemoglobin in there. Remember, that is the oxygen binding molecule found in red blood cells. Well, this is like a special kind of hemoglobin. In a sense, this leg hemoglobin, it still binds oxygen. But the reason it's binding this oxygen is actually to protect nitrogenous. That enzyme that's going to carry out, uh, the chemical reaction that turns gaseous nitrogen into ammonia. It's gonna protect that enzyme complex from oxygen poisoning. So it's just one more way in which plants are actually helping out these rise obeah bacteria. Now, I also mentioned that these bacteria weren't the Onley way that plants can obtain nitrogen. And I mentioned to try divorce. And, of course, when you think to try divorce, hopefully you're thinking fun guy. Obviously, bacteria play a role, uh, in the breakdown of organic matter as well, definitely not going to discount how important bacteria are. But these, um, these fungi will form. Remember, my core is I those fungus roots those associations between the fungal hi fi and the plant roots, and in this association they will actually be able thio provide nutrients for the plants like nitrogen and phosphorus both super important, right? Both gonna wind up components of nucleic assets, for example. Now the high fe increase the surface area for absorption. So they're gonna help plants absorb nutrients better. They also, uh, you know, the fungus also will break down organic matter, which is going to free up these elements for absorption. Right? They're gonna help break down structures that they're part of making them easier for plants to absorb. And we're actually going to see two types of micro, is I. There's Ecto Micro is I Which I have pictures of here. And basically, this is micro's I where the haIf a wrap around plant cells but don't actually penetrate into plant cells. So these are not end of fights. Our bus killer Micro is I, on the other hand, are end of fights. They're going to actually penetrate their hi fi into the cortical cells of plant roots. And I don't have a picture of that here. But, you know, you can imagine looking at this image here, for example, that one of these purple haIf A would extend into a plant cell in the Arbus secular micro is I, um, hear what I actually have pictures of our Ecto Micro, is I? So this is a more resumed out image. These brown twiggy looking things are plant roots and all this white gunk all over it. That kind of looks like mold is the is the fungal part of the micro. Is I So you can see, um, you know, with the naked eye basically that close association of plant and fungus. Here we have some mawr zoomed in pictures like right here and especially right here, here. We're looking at, you know, a fungal sheath around the route. And here in this image that's behind my head. You can actually see thehyperfix wrapped around plant cells. These dark spots are going to be the actual cells of the plant and all this white gunk in between them is the high face, so that that's the fungus part of it. So this close association, uh, not only helps plants absorb nutrients but can also help provide some nitrogen phosphorous for plants. And also, don't forget that there's just a bunch of other fungus in the soil free living that's also breaking down organic matter and contributing to the amount of free nitrogen available in the soil. That's all I have for this lesson. I'll see you guys next time