Muvirus

VIRION

Non-enveloped, head-tail structure. The icosahedral head is about 54 nm with a knob-like neck. The tails is contractile, has a baseplate and 6 short fibers.

GENOME

Linear, dsDNA genome of about 40 kb, encoding for 56 proteins. 50-150 bp and about 2 Kb of bacterial DNA are respectively covalently linked at the left and the right end of Mu genome. The presence of these pieces of bacterial DNA is due to the headful packaging mechanism.

GENE EXPRESSION

Genes are transcribed by operons.

REPLICATION

CYTOPLASMIC

  1. Adsorption: the phage attaches to the target cell lipopolysaccharides (LPS) through its tail fibers. Two types of fibers are encoded by the phage to allow receptor tropism switching.
  2. Ejection of the viral DNA into host cell cytoplasm by contraction of the tail sheath.
  3. Viral DNA ends are protected from degradation by host nucleases.
  4. ?Transcription and translation of early genes?
  5. Circularization and supercoiling of the viral DNA.
  6. Integration of viral DNA into the host chromosome.
  7. Replicative transposition gives rise to 50-100 new copies of the viral genome in the host chromosome.
  8. Transcription and translation of late genes.
  9. Assembly of an empty procapsid.
  10. Momylation of viral DNA (modification of adenines) makes the packaged viral DNA resistant to host restriction enzymes.
  11. Viral tail fibers assembly and viral tail assembly.
  12. Mature virions are released from the cell by lysis.