In this video, we're going to introduce lysogenic conversion. Lysogenic conversion is really just a phenotypic change of a lysogen based on the prophage that it carries. Once again, recall from our previous lesson videos that a prophage is really just the integrated phage DNA, and the lysogen is the cell that contains the prophage. Lysogenic conversion occurs when the lysogen changes its phenotype due to the integrated phage DNA, the prophage. Typically, lysogenic conversion can result in the change of the host cell surface structures. These host cell surface structures are what the phages rely on to attach and initiate an infection. By changing the host cell surface structures, the phages will not be able to attach. Thus, cells can become immune to what is known as superinfection, which is really just infection by the same type of phage. When lysogenic conversion changes the host cell surface structures, the same phage will not be able to infect the cell, making the lysogen immune to superinfection.
Occasionally, lysogenic conversion can also give the cell disease-causing properties. For example, the synthesis of a toxin, the ability to synthesize a toxin. Let's take a look at our image down below to get a better understanding of lysogenic conversion. On the left, we're showing you a bacterial cell, and before a viral infection, we have a bacterial cell with a normal phenotype. However, notice that when a bacteriophage virus comes and infects the cell and injects its genome, that genome occasionally can insert itself into the chromosome to create a prophage, which is what we're showing you here. The prophage is the integrated phage DNA. Notice that the surface receptors of this lysogen are capable of being converted through lysogenic conversion to alter the phenotype. Over here, we have an altered phenotype where now the surface structures are being altered through the prophage. The alteration of these surface structures makes it so that the same phage is not able to bind and induce an infection. This lysogen with an altered phenotype due to lysogenic conversion is going to be immune to a superinfection or immune to infection by the same phage. In addition to superinfections, sometimes lysogenic conversion can give these lysogens disease-causing properties, like, for example, the ability to synthesize a specific type of toxin.
This here concludes our brief introduction to lysogenic conversion, and we'll be able to get some practice applying these concepts as we move forward in our course. So I'll see you all in our next video.