Structure of Bacteriophage


The group of viruses which attacks bacteria was first described in 1915 by the British scientist Twort. Bacteriophages are filterable and will grow only in the presence of living cells in bacteria which they cause to swell and dissolve. Bacteriophages are found in nature wherever bacteria occur. They are especially found in abundance in the intestines of man and other animals.

Structure of Bacteriophage:

They are several varieties of bacteriophages. Usually, each kind of bacteriophage will attack only one species or even only one strain of bacteria. Electron micrographs revealed that the bacteriophages may be spherical or comma-shaped or may have a tail. They are about 5 μm in diameter.

The initial step in viral reproduction is the attachment of the virus to the bacterial cell by means of its protein tail. An enzyme found in the tail digests part of the bacterial cell wall and the deoxyribonucleic acid (DNA) found in the core of the virus passes into the bacterial cell.

Hershey and Chase have shown that only the DNA of the virus is injected into the bacterium while the protein coat of the head and tail don’t enter. The inference is that the DNA contains all the genetic information for the synthesis of the complete virus particle. The DNA directs the biosynthetic system of the host cell to produce viral DNA and viral protein.