Phager

Phager is not a standard term in modern biology; when encountered, it most often refers to a bacteriophage, or phage, a virus that infects bacteria. The preferred term is phage or bacteriophage, while "phager" may appear as a variant spelling or in non-English contexts. Bacteriophages are highly diverse and widely distributed in nature.

Most phages have a protein capsid enclosing their genetic material, and many possess a tail used to attach to bacterial cells. Their genomes can be made of DNA or RNA, and may be single- or double-stranded. Phages typically infect specific bacterial hosts, determined by receptor recognition, giving them a narrow host range.

Life cycles: The two main strategies are lytic and lysogenic. In the lytic cycle, phages replicate rapidly, hijack the host's machinery, and cause cell lysis to release progeny. In the lysogenic cycle, the phage genome integrates into the bacterial chromosome as a prophage and can be inherited with cell division; under stress, the prophage may activate to enter the lytic cycle.

Ecology and applications: Phages shape microbial communities, contribute to horizontal gene transfer, and are explored for phage therapy to treat antibiotic-resistant infections, as well as for biocontrol and biotechnology. Phage display, a related technique, uses phages to study protein interactions. Regulatory and safety considerations influence clinical use globally.

History: Phages were discovered independently in 1915 by Frederick Twort in Britain and in 1917 by Félix d'Herelle in France. Since then, research on phages has advanced microbiology, genomics, and therapeutic approaches, although clinical adoption varies by country.