T4 phage
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Phages are compound and consist of a head and a tail. Virions are not enveloped. Head separated from tail by a neck, tail complex, consisting of a central tube and a contractile sheath, provided with a collar, base plate, 6 short spikes and 6 long fibers. The phage has a head with icosahedral symmetry and a tail with helical symmetry. The head displays icosahedral symmetry, or symmetry which is derived from a basic icosahedral structure by adding rows of capsomers. The head is isometric in shape and has a diameter of 50110 nm. The capsids of this particular phage are hexagonal in appearance. The capsid consists of 152 capsomers. The tail is tubular, long; contractile, rigid; is crossbanded, or is diagonally striated with a crisscrossed appearance of (80) 95111(455) nm; tail thick; 1620 nm in diameter. Axial canal is distinct; basic helix is obvious...