VIRION

Non-enveloped, head-tail structure. Heads are about 84-94 nm in diameter and and tails 140-219 in length. The tail is contractile with globular structures at its tip, has 6 long terminal fibers, 6 short spikes and a double base plate. The capsid has a T=16 symmetry (SPO1-like viruses).

GENOME

Linear, dsDNA genome of 130-140 kb, encoding for about 190-215 proteins.

GENE EXPRESSION

Genes are transcribed by operons. Some Twortlikevirus might have circularly permuted genomes.

REPLICATION

CYTOPLASMIC

  1. Adsorption: the phage attaches to the target cell through its tail fibers.
  2. Ejection of the viral DNA into host cell cytoplasm by contraction of the tail sheath.
  3. Transcription and translation of early genes.
  4. Replication of genomic DNA. Transcription and translation of late genes.
  5. Assembly of an empty procapsid and packaging of the genome.
  6. Viral tail fibers assembly and viral tail assembly.
  7. Mature virions are released from the cell by lysis.