phagenDNA

PhagenDNA refers to the genetic material contained within bacteriophages, the viruses that infect bacteria and archaea. In most well-characterized phages, the genome is composed of double-stranded DNA and is packaged within a protein capsid, though small single-stranded DNA phages and RNA phages exist. PhagenDNA encodes the information needed to replicate the virus, assemble particles, and lyse or otherwise exit the host cell.

Genome organization in phages is highly modular, with clusters of genes dedicated to replication and regulation, structural components (capsid and tail fibers), DNA packaging, and lysis. Genome sizes vary widely—from a few kilobases in small ssDNA phages to over 200 kilobases in large dsDNA phages. Some genomes have terminal repeats or are circularly permuted, reflecting diverse replication and packaging strategies.

Life cycles of phages include the lytic cycle, in which phagenDNA is replicated and new virions are produced leading to host cell lysis, and the lysogenic cycle, where the phage DNA integrates into the host genome as a prophage and propagates passively with cellular division. Under certain conditions, prophages can reactivate and enter the lytic cycle. Replication involves phage-encoded enzymes and host factors, and DNA is packaged into preformed capsids by terminase complexes, sometimes using headful mechanisms.

Diversity among phagenDNA sequences is substantial, with widespread mosaicism resulting from recombination and horizontal gene transfer. This genetic fluidity underpins rapid adaptation to bacterial hosts and environmental conditions, and it poses challenges for universal gene markers.

Applications of knowledge about phagenDNA include phage therapy, bacterial biocontrol, and tools for genetic engineering and biotechnology. Sequencing of phage genomes advances understanding of viral evolution and host-virus interactions.

See also: Bacteriophage, Phage therapy, Viral genomics.