P22

P22 refers to a bacteriophage that infects Salmonella enterica serovar Typhimurium. It is a double-stranded DNA virus of practical importance in molecular biology because of its well-characterized life cycle and morphological assembly. P22 is considered temperate, capable of both lytic replication and lysogeny under appropriate conditions, and has been used to study phage-host interactions, gene regulation, and genome packaging.

Structurally, virions display an icosahedral head and a short, non-contractile tail. The genome spans tens of kilobases and is organized into functional modules for early regulation, replication, and morphogenesis. The phage has been subject to extensive genetic and structural analyses, including studies on the portal complex, coat proteins, and scaffolding proteins that assist capsid assembly.

In biotechnological contexts, P22-based virus-like particles act as nanocontainers for cargo delivery and materials science research. The coat protein and scaffolding protein system can be engineered to assemble customizable shells around inert cargo, enabling applications in vaccines, imaging, and nanomaterials.

Due to its tractability, P22 remains a standard model in phage biology and is discussed alongside related P22-like phages that share similar architecture and regulatory logic.