Index >> Virus Structure and Classification >> Virus Complex Symmetry,Vaccinia Virus, Bacteriophages of T-Even Series (T2,T4,T6)

Virus Complex Symmetry, Vaccinia Virus,Bacteriophages of T Eveneries ( T2,T4,T6)

Complex viruses are divided into two groups: those without identifiable caps ids and those with capsids to which are attached, additional structures.

The vaccinia virus is an example of a virus without a definite capsid. The nucleic acid is surrounded by several coats.

Bacteriophages of the T-even series (T2, T4, T_) are examples of complex viruses with caps ids and attached structures.

The following description pertains to the T4 bacteriophage which grows in the colon bacterium Escherichia coli.

The tail consists of a core tube 80A in diameter, through Which DNA passes out, surrounded by a protein tail sheath. The sheath con­sists of 144 subunits arranged in 24 rings of 6 subunits each.

The sheath is connected to a thin disc, called the collar, at the upper end and a base plate at the lower end. The base plate is hexagonal, and has apin or spike at each corner. From each of the six corners is also given off a long, thin tail fibre, 1300A long, which serves for the attachment of the bacteriophage to the host cell.