Pbunavirus

VIRION

Non-enveloped, head-tail structure. Head is about 75 nm in diameter. The tail is contractile, about 140 nm in length with four short straight tail fibers and a baseplate that separates from the sheath upon contraction. The tail exhibits no transverse striations, but presents a criss-cross pattern.

GENOME

Linear, dsDNA genome of about 65-75 kb, encoding for 90-130 proteins.

GENE EXPRESSION

Genes are transcribed by operons. PB1 phages lack a phage-encoded RNA polymerase and they depend entirely on the host transcriptional machinery.

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 viral 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.