 Now, we will study the bacteriophages. We have already discussed about just a little bit Berzai view about the bacteriophages. Bacteriophages are very important viruses from the experimentally point of view. These are those viruses which are causing the disease or which are infecting the bacteria. So therefore, for the biological control, because the last antibiotic which was produced long, long years ago against the bacteria, so now we are towards the biological control of the different diseases, which is just the environmental friendly. Therefore, for the diseases which are caused by the bacteria, bacteriophages are the best treatments for the, because these are the viruses and these are causing the disease in the bacteria. Therefore, they are going to destroy the bacteria. We can use such kind of the bacteriophages against some kind of the bacteria to kill them. So, first of all, we will see the introduction. First of all, what is the bacteria, bacteriophages, bacteriophages are those viruses which infect and replicate in the bacterial cell and call the bacteriophages. These are morphologically diverse, very diverse viruses and some filamentous with the helical cemetery. Some of them are the helical cemetery and the filamentous and others are icosahedral. We will see the structure. Just here, you can see different parts of the, this is the helical infrastructure and most of them the icosahedral, this is icosahedral, this is its head and this is the body, the three parts and these are the filaments, the long legs. You can see here the base plates, the most of the things are head and tail, they are consist of the head and its tail and short legs are also there, so this is the neck and collar. That is icosahedral structure and containing the phage DNA, the phage DNA will be present inside its head. We will see in detail that how it should replicate and how it's caused the diseases. However, this is the very important to study that this virus has very simple structure and it's very easily can infect the bacteria. Genome is present, the DNA is present, genome is consist of the DNA or RNA and which are present inside the head of the bacteriophages. So replication, replication is just similar like the other viruses, it is started from the attachment of the viruses with the bacterial cell, there are the special receptors which are present on the host through which the virus will be attached on the cell wall or on the bacterial wall and then it will be penetrated, it will be enters inside the body and uncoating at the time of the entry, there is the uncoating, the virus should come out of its capsid, its wall and then DNA will be entered and then the biosynthesis and the replication and release of the DNA and RNA inside the body. We will see the bacteriophages replication and we will see the other characteristics of the bacteriophages in detail later.