Viruses in the former family
Podoviridae are non-enveloped, with icosahedral and head-tail geometries. The diameter is around 60 nm, and consists of 72 capsomers. The head protein has a molecular mass of ~38 kilodaltons and is present in 460 copies per virion. There are 9 structural proteins. The tail is non-contractile and has 6 short subterminal fibers. It is thick and rod-shaped and built of stacked disks. The maximum length is ~17 nm. The double stranded DNA genome is linear, around 40-42kb in length, and encodes ~55 genes. The
guanine +
cytosine content is ~50%. It has terminally redundant sequences and is nonpermuted. By weight, the genome constitutes ~50% of the viron. The genome encodes 9 structural proteins, an adenylated transferase B type DNA polymerase and an RNA polymerase. Three internal proteins constitute the polymerase complex. Two classes of genes are recognized (early and late). This classification is based on the timing of transcription that is temporally regulated. Genes with related functions are clustered together. Genome replication is bidirectional. ==Life cycle==