Non-enveloped, head-tail structure. The capsid is about 84-94 nm in diameter and has a T=16 icosahedral symmetry (Spounalikevirus) . The tail is 140-219 in length, contractile with globular structures at its tip, has 6 long terminal fibers, 6 short spikes and a double base plate.
Linear, dsDNA genome of 130-160 kb, encoding for about 190-230 proteins. Some Twortlikevirus might have circularly permuted genomes.
Genes are transcribed by operons.
- DNA-directed DNA polymerase family A palm
- Cysteine protease (Peptidase C51)
- Ribonucleoside reductase
- Adsorption: the phage attaches to the target cell through its tail fibers.
- Ejection of the viral DNA into host cell cytoplasm by contraction of the tail sheath.
- Transcription and translation of early genes.
- Replication of viral 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.