VIRION
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).
GENOME
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.
GENE EXPRESSION
Genes are transcribed by operons.
REPLICATION
CYTOPLASMIC
- Adsorption: the phage attaches to target cell through its tail fibers.
- Viral lysozyme degrades cell wall locally
- Injection: viral DNA is injected in host cell periplasm by contraction of the tail
- Transcription and traduction of early genes
- Replication of genomic DNA
- Transcription and traduction of late genes
- Assembly of new virions in host cell cytoplasm
- Mature virions are released from the cell by lysis