Bacteriophage: Lytic Phage Infections

in this video we're going to continue to talk more about bacteria. Fage is by focusing specifically on the lyric fage infections. And so recall from our previous lesson videos that the lyrics cycle is a productive infection, meaning that it allows for the production of new fe ages, allowing for lyric fage reproduction and increasing the number of lyric fage is now as its name implies, the lyric cycle ends up resulting in the list system of the host cell which will kill the host cell and release the newly produced fage is now the lyrics cycle actually occurs in a series of five steps that we have numbered down below in our image. And so if we take a look at our image down below, we can get a better understanding of this lyric cycle. And so in the very first step of the lyrics cycle, what we have is attachment. And in this step the fage is going to attach two very specific receptors on the host bacterium's uh cell envelope. And so what you'll notice is here we have our bacteria fage and down below we have our bacterial cell and inside the bacterial cell here we have the bacterial chromosome. And what you'll notice is that the very first step of the lyrics cycle is just for this bacteria fage to attach to the surface of the host bacterium by interacting with very specific receptors on the host bacteria. Then in step #2 of the lyrics cycle, what we have is genome entry. And so this is when the fage the bacteria page is going to inject its genome or its D. N. A. For example, into the host bacteria. However, it is important to note that the protein coat of the bacteria fage is not injected, it remains on the outside of the host cell. And so what you'll notice here in this image is we have our bacteria fage here and the protein coat of the bacteria fage remains on the outside of the host cell. However, the genome is going to enter into the host cell. And so the DNA here in this case the fage DNA is being injected into the host cell. Now in step # three of the lyrics cycle, we have synthesis. And so what happens is fage enzymes are going to be synthesized and those fage enzymes are going to degrade the host D. N. A. And so notice that the bacterial chromosome here uh in the synthesis stage it's being degraded and chopped up into a bunch of small pieces which essentially is going to inactivate the bacterial host chromosome. And in addition to that viral genome and viral proteins are going to be made. And so the fage proteins and genomes are going to be produced. They're going to be made in this synthesis step. Then in the 4th step, what we have is assembly. And in this assembly step, what happens is all of the fage components that were made including the fage proteins and the fage genomes are going to be assembled inside the bacterium to create more fage is. And so what you'll notice is that all of these different pieces of the fage are going to be assembled together to put together the entire fage and this occurs inside of the bacterial cell. And then finally in the 5th and final step of the lyrics cycle, we have release. And as its name implies, this is when the host cell is going to lice. And so the host cell lice is and as it lice is, it releases all of the newly infectious bacteria pages that were produced. And so you can see here the license of our bacterial cell is occurring the rupturing of the cell and all of these assembled bacteria pages are being released and they can go on to start a brand new lyrics cycle infection on another neighboring bacterial host cell. And so really this year concludes our brief lesson to lyric fage infections and the five steps of this lyric infection cycle. And we'll be able to get some practice applying these concepts and learn more as we move forward in our course. So I'll see you all in our next video