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 a little more formal, phages can be defined as bacterial obligate intracellular parasites, which means that they have to infect living bacteria and use the cell machinery of the living bacteria to replicate. These phages are made of either DNA or RNA packed into a protein coat.

These phages infect living cells, then they use the cellular machinery of those living cells to replicate, and then they ultimately end up lysing the cell or causing the cell to rupture. When the cell ruptures, it releases new phage particles, and those phage particles can be released and then initiate another infection of a different cell. Transduction involves horizontal DNA transfer using these bacteriophage viruses. It actually results from an error consisting of bacterial DNA accidentally being packaged into the phage instead of viral DNA being packaged.

When this error occurs and bacterial DNA is packaged into the phage, this creates what is called a transducing particle. A transducing particle is a defective phage that is carrying bacterial DNA instead of carrying 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. We have our cell here in this circle. Inside the cell, we have the bacterial DNA, the bacterial chromosome. The red structure you see here represents the bacteriophage. The bacteriophage, or just the phage, will attach and inject viral DNA into the bacterial cell.

Phage enzymes, which are also going to be injected, are going to cut the bacterial DNA. Notice that the bacterial DNA is being cut into a whole bunch of different pieces. Then, the bacteriophage DNA will replicate, and you can see that from one molecule of the phage DNA in green, we now have multiple molecules. In addition to the phage DNA replicating, viral proteins are also going to be made. More viral proteins represented by these red shells here will be formed. The transducing particle comes into play due to an error where bacterial DNA is accidentally packaged into the phage instead of viral DNA. Some bacteriophages are going to contain phage DNA in green, representing another virus that could conduct another viral infection. But sometimes, there is an error where the phage is packaged with bacterial DNA, shown by these little blue particles, which are phages containing bacterial DNA. These phages are referred to as transducing particles.

The transducing particle is 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 process is called transduction. This concludes our brief introduction to transduction and transducing particles.

As we move forward in our course, we will be able to continue to talk more about transduction. I'll see you all in our next video.