Non-enveloped, head-tail structure. Head is about 50-110 nm in diameter. The tail is contractile, has 6 long terminal fibers, 6 short spikes and a small base plate. The capsid has an elongated icosahedral symmetry T=13 Q=21, composed of 152 capsomers (T4 phage).
Linear, dsDNA genome of about 33-244 kb, encoding for 40-415 proteins, the peduoviruses being the smallest ones. Some species have a linear, circularly permuted genome.
Genes are transcribed by operons.
- Adsorption: the phage attaches to the target cell through its tail fibers.
- Viral exolysin degrades cell wall locally
- Ejection of the viral DNA into host cell cytoplasm by contraction of the tail sheath.
- Transcription and translation of early genes.
- Replication of genomic DNA. Transcription and translation of late genes.
- Assembly of an empty procapsid and packaging of the genome.
- Viral tail fibers assembly and viral tail assembly.
- Mature virions are released from the cell by lysis.