Structure and Shape of bacteriophage

These have two shapes (structural forms):

  1. Cubical:

These are regular solid or icosahedral (having 20 triangular faces).

  1. Helical Symmetry:

They are rod shaped. Many phages consist of head and tail. The heads are polyhedral but tails are rod shaped.


Bacteriophage meaning bacteria eater.

Earlier workers studied few phages that infect Escherichia coli. Of these the best phages are T phages (T for type).

Two main types of T phages are T2 and T4.


The structure under electron microscope looks like a tadpole and consists of head and tail.


The head is elongated having:

Pyramidal (having two triangular structures with common base), hexagonal or prism shaped structure to it straight tail is attached.

Head contains double stranded DNA.


The structure of tail is more complex than head.

Tail has a core of protein which is surrounded by a sheath of another protein.

On one side of the sheath is collar and on the other side is endplate (Baseplate).

Sixtailfibers are attached to the end plate. These fibers are for attachment.

Volume of the Phage:

It is about 1/1000 of the host.

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