Tectiviridae

VIRION

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Non enveloped, icosahedral virion with a pseudo T=25 symmetry. Virion size is about 66 nm with apical spikes of 20 nm. The capsid encloses a inner membrane vesicle within which the genomic DNA is coiled.
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GENOME

Linear, dsDNA genome of about 15 kb flanked by inverted repeats. Encodes for 30 ORFs. Replication is protein-primed.

GENE EXPRESSION

Genes are transcribed by operons.

REPLICATION

CYTOPLASMIC

  1. Adsorption: the phage attaches to target cell through its spike protein P2. As a result, a protein complex composed of P2, P5, P31 and a part of the capsid (p3) is released, which produces a hole in the capsid.
  2. Internal phage membrane transforms into a tubular structure that protrudes through the hole in the capsid and penetrates the host outer membrane and peptidoglycan layer, to fuse with host plasma membrane, releasing the viral DNA into cytoplasm.
  3. Transcription and translation of early genes.
  4. Replication of genomic DNA.
  5. Transcription and translation of late genes.
  6. Capsid proteins polymerize around a lipoprotein vesicle translocated in the cytoplasm by virion assembly factors.
  7. Genomic DNA is packaged in new virions.
  8. Mature virions are released from the cell by lysis.