Prokaryote Reproduction and Gene Exchange

Hi. In this video we'll be talking about how precarious reproduce and exchange genetic information now precarious. Reproduce a sexually and they actually congrats. Oh, at an exponential rate if provided the right conditions and the right nutrients. And what you can see here is a chart of the growth of a colony of bacteria. And we have this burst here of exponential growth, right, That's called the exponential phase on. You know, theoretically, this could go on forever. But generally speaking, um, the bacteria will exhaust the nutrients, or they will grow to the point where there's not enough space left in the environment. You know, something will cause their growth to actually level off, and eventually, you know, without nutrients and whatever, they'll start to die. Um, we don't really need to worry too much about this. The main point that I want to make is that bacterial growth can get exponential. And the reason for this is that bacteria reproduce a sexually through a process called binary fission. Right. So one cell will produce two cells. Those two cells will each produce two more cells. So, you know, starting with one cell, you'll get like, one than 248 16, 32 64. So on it gets very large, very quickly. Now, this process of binary fission results in two identical daughter cells. So right here we have our two daughter cells. Sorry, it's a really ugly you. There we go, daughter cells. Um, and basically this, you know, parental cell, if you will, is going to replicate its genetic information grow and divide into these two identical cells that will each receive a copy unidentifed copy of the chromosome and whatever plasmids might be present in the parent cell. So the point is, through binary fission, you do not really get genetic variation. Now, that's sort of the the theory. In actuality, bacterial genes undergo a pretty significant frequency of mutation, meaning that the rate at which mutations air introduced, um, during replication, which again is through binary fission, is actually significant enough thio, um, to impact evolution And the reason for this, um, the reason that thief frequency of mutation has a significant impact is due to the short generation times on large populations of bacteria. So essentially, because the cells can, um, you know, divide and those daughter cells will get to the point where they can reproduce in such a short window of time. That that is to say, the generation time the time it takes to produce a new generation is so small, so short. Um, and also the populations of bacteria that exist are so large. There's so many individuals in the population that we actually do see a significant frequency of mutations, even though, um, you know, even though there are no mechanisms in place during binary fission that allow for genetic variation like there are in sexual reproduction, right, that's really the basis of comparison here in sexual reproduction. You know, like we talked about back in the genetic section. You can have, uh, you know, a lot of variation due to things like Crossover, for example. Now, uh, there are ways in which pro cario it's you can introduced genetic variation. It just doesn't happen through the reproduction process doesn't happen through binary fission. There are alternative ways. The main thing I was trying to say is that through binary fission alone, there actually is a decent amount of genetic change over time, and it is again due to the high frequency of mutation, which is a result of those large populations and short generation times. Now, um, uh, really kind of crazy if you think about it. Way that bacteria, um are precarious in general can introduce. Uh, genetic variation is through a process called transformation. And this is essentially when a cell alters its genetics by incorporating exogenous DNA meaning DNA found outside the cell so the cell will literally take up DNA from outside the cell, like, literally could just take up a piece of DNA that's just lying around. It'll take it into the cell and incorporate it into its own genome or plasma or whatever, and this will result in genetic variation in the cell. Right. So we have a little example of this going on right here. You can see this cell is going thio, you know, lose or whatever introduced the environment, this little piece of DNA and then this other cell here is going to take it up and incorporated into its plasma. Right? So this cell right here, his transformed by this piece of DNA over here and what's pretty cool about transformation is not only will this is, you know, can this occur between the same species, but it can occur between different species. Um, it it actually, you know, the it can cross, um, pretty far species boundaries in actuality. So it's pretty, pretty awesome and kind of crazy if you think about it, you know, just pick me up random DNA from the environment. Pretty crazy way of introducing genetic variation. Now, viruses, believe or not, can also play a role in introducing genetic variation into pro carry its And actually, they can also introduce, um, introduce genes into you carry outs. But this is that's a different process. Has a different name. We're not really gonna talk about it here. Um, I will mention so in pro Kerasiotes. We call it this process. Trans duck shin, where DNA is transferred from one bacteria cell to another by a virus. When DNA is transferred into eukaryotes through a virus, it's called trance faction. Right. I think I'm just gonna write that down Trans infection. Kind of like infection. Right? Because you're using a virus, you're infecting cells, and then they're transferring some DNA to those cells. So trance fiction, remember? That's, uh, what happens in you carry outs and again, we're not going to get into how that process works. So looking at Trans Duck shin basically the way this can work is you know, let's say, uh this bacterial cell gets infected. Here we have a nice little bacteria Fage. Here's our bacteria Fage and it is going to you can see it's it's got that DNA and pink in the caps it right there. It's gonna introduce that DNA into the cell. You can see here in the cell there are those pieces of viral DNA and you might also notice that the, uh, bacterial DNA has been decomposed, right? That's part of what the virus is gonna do to the cell. And it's the viruses DNA, that is, is going to be used to build mawr viruses. And that's what we see happening here. But what's crazy sometimes, right, because viruses, they're like little simple machines, kind of if you think about it and they're gonna make mistakes, and sometimes they're gonna pick up some bacterial DNA in the viruses that they produce. So you can see here. This is you know, this virus right here is basically a copy of the original bacteria. Fade right. This one not only has viral DNA also has some bacterial DNA. And if this if this bacteria fage right here, if this one goes on to, in fact, to sell like we see happening here, not only is it gonna introduce that viral DNA, right, it is going to introduce some of that bacterial DNA from this other previous bacteria over here. And what can happen is that bacterial DNA can actually you can see it can get incorporated into the chromosome or potentially plasmid in this other pro carry attic cell. So viruses can act as what's called a vector, right? They can act as a means of moving some DNA from one bacterial cell, thio some other bacterial cell. And again, this can happen between species or within the same species. Um, s o these two methods we just talked about transformation and transaction are ways in which bacteria can introduce genetic variation into their populations by incorporating external DNA into their cells, either by picking it up from the environment or by, you know, having a virus. Transfer it as you know, through a viral vector. All right, let's turn the page

so the last way that pro Kerasiotes can introduce genetic variation is through what's known as conjugation. And this is unlike the other methods. We discussed a direct transfer of genetic material between two physically linked bacterial cells. And this is going to involve that appendage we previously discussed. Called a pill us the plural of that. In case you're curious, Pillai, that's the plural form of pillows. Ah, you know, Latin words. Gonna have strange forms to them. Anyways. A eso This is an appendage used thio connect the two cells that are going to be involved in conjugation. And really, what this all boils down to is the presence of this special plasma called the F plasma. And, um, this plasma actually can become incorporated, uh, into the chromosome, the actual chromosomal DNA of a cell. So really, uh, it's probably better to just call it the F factor, right? That that, uh, term F factor can both mean the f plasma and also theme the all right, you know, f plasma genes having been incorporated into the chromosomal DNA. So essentially, these air just a bunch of genes required for this genetic transfer. So, um, it in order to have conjugation. You need what's called an f positive bacteria f plus. And basically, this is just a bacteria that possesses the F plasmid. Um, you can also have this F prime bacteria. You see that little symbol right there? That's prime. And these are bacteria that have the F factor incorporated into their bacterial chromosome. Right, So you need either F plus or F prime. You also need an F minus bacteria or, uh, a bacteria that is lacking the F factor and is going to act as a recipient of the genes. Right. So, uh, the bacteria that has the F factor is going to pass on the jeans and bacteria that lacks it is going to receive them. So looking at our little model here, basically you have the what's called the donor, and it is going to extend its pillows. And guess what? The genes for that pillows are part of the F plasma. Go figure. Right. Um, so it's going to connect to the recipient cell, and from there the two are gonna be linked. The pillows is actually going to kind of pull them together. Uh, there's gonna be a opening between the cells and the genetic information is going to be transferred. You can see from the donor cell into the recipient cell there. And at that point, that sell that receives the F plasma is going to, um, become a cell that is now capable of acting as a donor and let me hop out of pictures so you could see that. Yeah. So it is now going to be a F plus cell, right? This one was f plus the whole time. This is newly F plus says F plus old f plus Knew what everyone call it old donor. New donor. Right. So now this new donor, now it can make its own pillows right? Because now it has the genes, too. So this is sort of a very simplified version of what goes on during conjugation and again, The main idea is that it involves direct gene transfer from a cell that contains the F factor to a cell that does not contain the F factor. Now, uh, there is a sort of special a case of conjugation that involves what's called in our plasma, and this is just a plasmid. I shouldn't say just but it's It's a plasma that carries a gene that will confer antibiotic resistance. So that's why I say I shouldn't say just these air, actually, super important. Uh, antibiotic resistance is like, you know, probably the most important topic in microbiology right now. Um, because, you know, there are many species that are becoming resistant to most forms, if not all forms of antibiotics that humans have developed. So, um, on our plasma is just plasma that can that carries the gene. That convert confers some type of antibiotic resistance. Uh, it's worth noting that not on Lee can these, um, be transferred via conjugation. But our our plasmids can also be transmitted by transformation and trans duck shin. All right, that's all I have for this video. See you guys next time.