In this video, we're going to talk more details about specialized transduction. Recall from our previous lesson videos that specialized transduction is one of two main types of transduction, and this is going to be a type of transduction in which the transducing particle contains both bacterial and phage DNA. Unlike generalized transduction, which transfers any of the general genes of the bacterial chromosome, specialized transduction can only transfer very specific or very specialized genes of the donor or bacterial cell. The genes that can be transferred are going to be the ones that allow for the formation of what's called a prophage. What happens is the bacteriophage DNA is going to integrate into the donor cell's chromosome to generate what's known as a prophage. A prophage is basically just when the phage DNA is integrated into the cell's chromosome. Ultimately, the prophage is going to be excised or removed. Occasionally when the prophage is excised, part of the donor cell's chromosomal DNA can be excised with it. You end up getting a molecule that has both phage DNA and bacterial DNA. The phage assembly ends up producing transducing particles that contain or carry both phage DNA as well as bacterial or donor DNA. Ultimately, the transducing particle will go on to inject the bacterial DNA, which is going to integrate into the recipient cell's chromosome, and the phage DNA is going to be degraded. This allows for the transfer of a gene from one cell to another cell. These genes, once again, are going to be very specific or specialized genes, not just any general gene.

If we take a look at this image below, we can get a better understanding of specialized transduction. Notice on the far left, what we're showing you is the original bacteriophage infecting a cell. The phage DNA is going to enter into the donor cell here, and then the phage DNA is going to have the ability to integrate and form what we call a prophage. Now we've got the phage DNA, which is in green, integrated into the bacterial chromosome, and we call this the prophage. Ultimately, this prophage is going to be excised. It's going to be removed. Occasionally when the prophage is excised, it will also remove with it a part of the donor cell's DNA or part of the bacterial chromosome's DNA. You can see that when the phage DNA is excised, when the prophage is excised, it can take with it part of the chromosome's DNA as well. The excised DNA contains both bacterial and phage DNA in a single molecule. When the transducing particles are formed, they are going to be carrying both phage and donor DNA or bacterial DNA. These are going to be transducing particles, and notice that these transducing particles contain both phage DNA and bacterial or donor DNA. When the cell lysis here, these transducing particles can be released and then they can go on to a neighboring cell, which would be a neighboring recipient cell, and it can basically bind to the recipient cell and inject the DNA that has both phage and bacterial DNA. Then, the donor DNA that is injected will integrate whereas the phage DNA is going to be degraded. You can see the phage DNA is being degraded over here whereas the donor DNA will actually integrate into the recipient cell's chromosome. What we're seeing is that donor DNA from the original cell is being transferred over to a recipient cell, and this transfer of this gene is occurring via a transducing particle. This is transduction, and once again this is specialized transduction because only very specific or specialized genes will be transferred in this way. Really, it's only going to be the ones in which the genes the prophage can form. If the prophage can form within the gene, then it will be able to be excised and be transferred via specialized transduction. The prophage cannot form in all genes, and that's why it's not general and not any general gene can be transferred. Only very specific and specialized genes can be transferred. This concludes our brief introduction to specialized transduction, a transducing particle containing both bacterial and phage DNA and only transferring very specific or specialized genes. We'll be able to get some practice applying these concepts as we move forward, so I'll see you all in our next video.