bacteriovirui

Bacteriovirui, commonly called bacteriophages or phages, are viruses that specifically infect bacteria. They are widespread in nature and influence bacterial populations and gene exchange. Bacteriovirui do not infect archaea or eukaryotic cells.

Structure and genomes: Most characterized bacteriovirui are tailed phages with icosahedral heads and tails, classified in Caudovirales as Myoviridae, Siphoviridae, or Podoviridae. Non-tailed and filamentous forms also exist. Their genomes are typically double-stranded DNA, though RNA phages occur. Genome sizes range from a few kilobases to over two hundred kilobases, often with cohesive ends or circular permutation.

Life cycles: Bacteriovirui can follow lytic or lysogenic lifecycles. In lytic cycles, infection leads to genome replication, virion production, and host lysis. Temperate phages can integrate into the bacterial chromosome as prophages, enabling vertical transmission; stress can induce a switch to lysis. Some phages cause chronic or pseudolysogenic infections.

Taxonomy and examples: Notable examples include T4 (Myoviridae), lambda (Siphoviridae), and T7 (Podoviridae). M13 is a filamentous phage used widely in molecular biology. Phage diversity is extensive and rapidly expanding with metagenomics.

Ecology and applications: Bacteriovirui regulate microbial communities in oceans, soils, and the human microbiome. They have potential in phage therapy and biocontrol, particularly as alternatives to antibiotics, and as tools for bacterial typing and genetic engineering. Safety concerns include horizontal gene transfer and regulatory considerations.

History: The concept of bacteriophages emerged in the 1910s through work by Frederick Twort and Félix d'Hérelle.