Podoviruses

Podoviruses are a group of tailed bacteriophages distinguished by their short, noncontractile tails and icosahedral capsids. In traditional taxonomy they formed the family Podoviridae within the order Caudovirales, though modern classifications emphasize shared features among tailed dsDNA phages. Morphology is characterized by a relatively small capsid, typically about 60 nanometers in diameter, and a short tail, usually 10–20 nanometers long, that lacks the contractile sheath seen in myoviruses. Some podoviruses possess tail fibers or baseplates that determine host recognition.

Genomes of podoviruses are commonly linear double-stranded DNA, generally in the range of 20–70 kilobases. They encode a compact set of genes for DNA replication, transcription, head and tail assembly, and lysis. Packaging often involves a terminase that cleaves and packages the genome; some members have distinctive features such as terminal proteins used to protect and initiate replication (for example, phi29).

Most podoviruses are lytic, producing new virions rapidly after infection and lysing the host cell to release progeny. They infect a variety of bacterial hosts, with host range typically restricted to specific strains or species. Notable examples studied in depth include Escherichia coli phage T7 and Bacillus subtilis phage phi29; Pseudomonas and Salmonella-infecting podoviruses are also described.

In application, podoviruses have been important as model systems for phage biology and are explored for phage therapy and biotechnological tools, including models for understanding tail–host interactions and, in some cases, phage-derived enzymes used in molecular biology.