In this video, we're going to begin our lesson on transduction. Recall from our previous lesson videos that transduction is another type of horizontal gene transfer or horizontal DNA transfer that occurs between cells and is mediated by what are known as bacteriophage viruses, otherwise just known as phages. Bacteriophages, or just phages, are viruses that infect bacteria. To be more formal, phages can be defined as bacterial obligate intracellular parasites, which means they have to infect living bacteria and use the cell machinery of the living bacteria to replicate. These phages or bacteriophages are made of either DNA or RNA packed into a protein coat. They infect living cells, then use the cellular machinery of those living cells to replicate, and then ultimately end up lysing the cell or causing the cell to rupture. When the cell ruptures, it releases new phage particles, which can then initiate another infection of a different cell. Transduction involves horizontal DNA transfer using these bacteriophage viruses. It results from an error consisting of bacterial DNA accidentally being packaged into the phage instead of viral DNA. When this error occurs and bacterial DNA is packaged into the phage, this creates what is called a transducing particle. A transducing particle is defined as a defective phage that carries bacterial DNA instead of its own viral DNA. This bacterial DNA can then be horizontally transferred to another organism.
Let's take a look at this image below to get a better understanding of the production of these transducing particles. Once again, we have our cell. Here is this circle. Inside the cell, we have bacterial DNA, the bacterial chromosome. This red structure represents the bacteriophage. The bacteriophage, or just the phage, is going to attach and inject viral DNA into the bacterial cell. You can see the phage DNA being injected here. Phage enzymes, which are also going to be injected or generated, will cut the bacterial DNA into many pieces. As the bacteriophage DNA replicates, you can see that initially there was just one molecule of phage DNA in green, and now we have multiple molecules. In addition to the phage DNA replicating, viral proteins are also being made, represented by these red shells. The transducing particle comes into play due to an error where bacterial DNA is accidentally packaged into the phage instead of viral DNA. Over here on the left-hand side, you can see that in some cases, an error occurs where bacterial DNA is packaged into the phage. Ultimately, the cell will lyse to release the particles. You can see the cell is lysing or rupturing, with phage DNA in green. This would be another virus that could conduct another viral infection. However, sometimes there is an error where the phage is going to be packaged with bacterial DNA, which these little blue particles represent. These phages that contain bacterial DNA are referred to as transducing particles. A transducing particle is really just a virus, a phage, that contains bacterial DNA. When this transducing particle goes to initiate another infection for a different cell, it will be injecting bacterial DNA instead of injecting phage DNA. This is how genes can be transferred between different bacteria using bacteriophages. This is called transduction.
This concludes our brief introduction to transduction and transducing particles. As we move forward in our course, we'll continue to talk more about transduction. I'll see you all in our next video.
