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
- Adsorption: the phage attaches to the target cell through its tail fibers.
- Ejection of the viral DNA into host cell cytoplasm by contraction of the tail sheath.
- Transcription and translation of early genes.
- Replication of viral DNA. Transcription and translation of late genes.
- Assembly of an empty procapsid and packaging of the genome.
- Viral tail fibers assembly and viral tail assembly.
- Mature virions are released from the cell by lysis.