Lytic and Lysogenic Cycles

by Jason Amores Sumpter
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bacteria, Fage actually can use two different types of cycles to replicate themselves, and here we're actually going to talk about both. Now, the first one we're going to talk about is the light IQ cycle, and this is fade replication that ultimately results in the death of the host light IQ. That term you see there, think of that as lice, right? When a cell bursts open, this cycle is going to result in tons of viral replication that actually will basically fill up the cell to the point of bursting. And it's going to lice burst open with all those viruses, release them to the environment so that they can infect other cells. So the light X cycle scroll down a little bit actually begins with the injection of the viral genome, as you see right here. So just label this number one. Now the bacteria Fage injects its viral genome into the cell, and then it will incorporate into the host cell's genome. Like you see, right here here we have the viral, and here is the bacterium's going abbreviate that backs. That's the bacterial portion that was originally in the cell. That's the bacteria's jeans and the viruses actually going Thio cause its own genes to be replicated, and it's actually going to degrade the host genome so that Onley its genes are being produced. And you can see that happening over here in this third image in the sequence now from its replicated genome, it's going thio, uh, lead to the production of caps and years, right, those components necessary to build new viruses. So here we can see some caps Amir's being produced, and eventually all the components will be produced like we see here in image number five. And from there they will spontaneously assemble into Fage is and those pages will lice from the cell like we see here in image number six. That is the basic those air, the basics of the light X cycle. A couple things to note. A. A virulent Fage is a fage that replicates by the light X cycle on Lee. Now there are there are many Fage is which can enter either cycle and can actually switch between them. But there are some that Onley used the light X cycle, and we call those virulent pages now. It's also worth noting that bacteria aren't total suckers to this. They've been around the block for a really long time, right? Billions of years, in fact. So bacteria actually have defensive mechanisms against these bacteria pages, and those come in the form of restriction enzymes that actually degrade the viral DNA that enters the host cell. Now the other cycle is the lice a genic cycle, and this involves replication of the viral genome without actually killing the host cell. As a result, we refer to Fage. Is that air capable of replicating through both lighting and Lissa genic cycles? Temperate pages, right? They're more tempered. They haven't more even temper, let's say, because they can kill off the host cell when they want to replicate a bunch of viruses. But they can also coexist with the cell without actually really harming it too much. So let's say those temperate pages arm or even tempered. Now, how does the Lissa genic cycle actually go down well again? First, Thief Age inserts its DNA into the host, just like we saw before. So this is still our first image of the lycee genic cycle, and again, the second is are The second phase is when the viral genome inserts itself into the bacterial genome. But now, instead of actually degrading the bacterial genome and replicating its own genome, the viral genome more or less lays dormant. And it allows the bacterial cell to replicate its own genome along with the viral genome, which is what we see happening here. You see how the bacterial genome is replicating normally, but because the viral genome has been incorporated into it, the viral genome is getting replicated, kind of like getting a free ride. And, of course, the bacteria will replicate its genome and eventually divide in a process that we know as binary vision, which we can see right here we have to jot er bacterial cells. Now each has that viral genome incorporated into its own genome. And eventually what will happen is at some point the virus will say, Well, not gonna lie dormant forever. And it will enter the light X cycle going from this image, five more or less back into to like we see here. And from there it will follow the light X cycle that we traced before couple points of terminology. Pro fage a pro fage is when the viral DNA has been integrated into the bacterial chromosome. And you can kind of think of this as the term pro fe, just kind of being like pre fage, right? Um, that that prefix pro means before kind of. So this is like a proto fage. In a sense, it's the precursor to the actual fage, um, so these two cycles can feed into each other. As we saw, the lycee genic cycle will feed into the light X cycle. At some point, however, the lice of genic cycle cycle can repeat itself many, many times, so that from one single infected bacteria there could be hundreds. Hundreds of bacteria with pro fage inside, laying dormant, waiting to enter the light X cycle and replicate all the necessary caps. Amir's self assemble a bunch of new bacteria pages and lice the cell to infect mawr host cells. All right, let's turn the page