Icosahedral T=21 capsid, 56 nm in diameter, composed of 1200 P1 (spike) and 60 P2 (capsid) proteins. The pentameric receptor-binding spikes are protruding from the 12 fivefold axes. The capsid encloses an internal lipid core containing the structural proteins P3 to P9.


Circular, supercoiled dsDNA genome of about 10 kb encoding for 21 proteins. Displays a very high number of negative supercoils.


The genome is organized in three operons.



  1. Adsorption: The phage attaches to target cell adhesion receptors.
  2. The capsid disintegrates and the inner capsid membrane is uncovered. This membrane then fuses with host outer membrane, releasing the viral DNA into the periplasm.
  3. penetration of the viral into the host cytoplasm.
  4. Transcription and translation of early genes.
  5. Replication of genomic DNA via a rolling circle mechanism.
  6. Transcription and translation of late genes.
  7. Capsid proteins polymerize around a lipoprotein vesicle translocated in the cytoplasm by virion assembly factors.
  8. Genomic DNA is packaged in new virions.
  9. Mature virions are released from the cell by lysis.