bacteriofaag

A bacteriofaag, or bacteriophage, is a virus that infects bacteria. Bacteriofaagi are diverse and ubiquitous, found in soil, water, and the microbiomes of many organisms. Most well-studied phages are tailed double-stranded DNA viruses that recognize specific bacterial receptors, attach via a tail fiber, and inject their genome into the host cell. They are typically highly host-specific, infecting only particular bacterial species or strains.

Phage life cycles are typically lytic or lysogenic. In the lytic cycle, the phage uses the bacterial machinery to replicate, assemble virions, and lyse the cell to release progeny. In the lysogenic cycle, the phage genome integrates as a prophage and is reproduced with the host; stress can trigger induction into lysis. Some phages, such as filamentous ones, produce progeny without destroying the host.

Bacteriofaagi have driven molecular biology. Model phages such as lambda, T4, T7, and M13 have provided key insights into gene regulation, replication, recombination, and assembly.

Phage therapy and biocontrol research explores using bacteriophages to treat bacterial infections or reduce pathogenic bacteria, particularly where antibiotics are ineffective. Phages also mediate horizontal gene transfer by transduction, contributing to bacterial evolution.

Environmentally, bacteriofaagi are abundant and influence bacterial population dynamics. They are studied as tools in genetics and biotechnology and as reservoirs of genetic diversity that shape microbial ecosystems.