Bacteriophage viruses, which grow as intracellular parasite of bacteria, are called Bacteriophages. It can be found in all types of bacteria. It has tadpole like shape with a hexagonal head and tail. The length of the head and tail is almost equal. It has a protein coat with a double stranded DNA. The tail is cylindrical made up of proteins. Basal end of the tail has a hexagonal spiked end plate. At each corner of the tail plate there is a thin tail fibre, which helps the phage particles for the attachment to its host. The upper end of the tail attached to the head by a narrow neck is known as collar.