VIRION
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Non-enveloped, head-tail structure. The prolate capsid is about 45 x 54 nm, with a T=3, Q=5 symmetry 
. The tail is non-contractile and has a collar with 12 appendages attached to the neck region that are important for host cell recognition and entry. The 55 capsid (head) fibers are not always present and may have been lost in some lab strains. They may enhance the attachment of the virions onto the host cell wall.
GENOME
Linear, dsDNA genome of about 16 to 20 kb encoding between 20 and 30 genes, with a terminal protein covalently attached at the 5' end.
GENE EXPRESSION
ENZYMES
- DNA dependent DNA polymerase [DNA pol]
- Protease (Peptidase G2) [Pre-neck appendage protein]
- Protein-primed terminal transferase [TP]
- Endolysin
REPLICATION
CYTOPLASMIC
- Adsorption: the phage attaches to target cell through its tail fibers.
- Ejection by short tail system: viral DNA is injected in host cell periplasm.
- Transcription and translation of early genes
- Replication of genomic DNA by strand displacement by the viral DNA polymerase, formation of viral genome concatemers.
- Transcription and translation of late genes
- Assembly of empty procapsids and viral genome packaging.
- Mature virions are released from the cell by lysis.