Environmental Microbiology of Aquatic and Waste Systems

4.1 Taxonomy of Microorganisms in Aquatic Environments 103

11 RuDIVIRIDAE

Structure
Non­enveloped, rod­shaped, rigid, with three tail fibers at either
end. Linear dsDNA genome of 32-35 kb. At both ends, there are
inverted terminal repeats as well as seven direct repeats. The two
strands of the linear genomes are covalently linked.

Host

Wide range of bacteria, Gram positive and Gram negative.

12 SIPHOVIRIDAE

Siphoviridae are a family of double­stranded DNA viruses
infecting only bacteria that are characterized by a long non­con­
tractile tail and an isometric capsid (morphotype B1) or a prolate
capsid (morphotype B2).
The Siphoviridae viruses have a capsid with a diameter of
about 55­60 nm and a long tail that can reach up to 570 nm.
Their double­stranded DNA is linear.

Nonenveloped, head­tail structure. The head is about 60 nm

in diameter. The tail is non­contractile, has fibers, and is fila­

mentous. The capsid is icosahedral with a T=7 symmetry. Linear,

dsDNA genome of about 50 kb, containing about 70 genes.

Host

Wide range of bacteria, Gram positive and Gram negative.