bakteriofaage

Bakteriofaage, commonly known as bacteriophages, are viruses that specifically infect and replicate within bacterial cells. Their host range is usually narrow, often limited to a single bacterial species or strain, although some phages can infect multiple related species. The term derives from the Greek words “bakterion” (bacterium) and “phagein” (to eat).

The typical structure of a bacteriophage consists of a head or capsid that encases the viral genetic material, a tail mechanism for delivering DNA or RNA into the host cytoplasm, and sometimes tail fibers or spikes that recognize receptors on the bacterial surface. Phage genomes are diverse, ranging from single-stranded RNA to double‑stranded DNA, and can be linear or circular.

Bacteriophages reproduce via two primary life cycles. In the lytic cycle, the phage hijacks bacterial machinery to produce new virions, ultimately lysing the cell to release progeny. In the lysogenic cycle, the phage genome integrates into the host chromosome and replicates passively with bacterial division; under certain conditions, it can switch to the lytic cycle.

The discovery of bacteriophages in 1915 by Frederick Twort and independently by Félix d’Hérelle opened a new field of microbiology. Subsequent studies revealed their role in regulating bacterial populations, mediating gene transfer, and influencing microbial ecology.

Modern applications include phage therapy to combat antibiotic‑resistant infections, use as biocontrol agents in food safety, and tools for genetic engineering such as CRISPR‑Cas delivery systems. Phage display technology also provides a platform for antibody and peptide library screening. Despite their promise, clinical use of bacteriophages requires careful consideration of host specificity, immune responses, and regulatory frameworks.