Bakterioiden

Bakterioiden, commonly called bacteriophages or phages, are viruses that infect bacteria. They are among the most abundant biological entities on Earth and influence bacterial populations, gene transfer, and nutrient cycling. Phages display diverse shapes and genome types, but all depend on bacterial cells to replicate.

Most bacteriophages consist of a protein capsid enclosing nucleic acid, with a tail that mediates attachment to bacterial receptors. Based on morphology, major groups include myoviruses (contractile tails), siphoviruses (long, noncontractile tails), and podoviruses (short tails). Their genomes are predominantly double-stranded DNA, though RNA phages exist in a few families. Some phages carry genes that modify host traits through lysogenic conversion when integrated as prophages.

Phages have lytic and lysogenic life cycles. In the lytic cycle, a phage attaches, injects its genome, uses the host machinery to produce new virions, and causes lysis to release them. In the lysogenic cycle, the phage genome integrates into the bacterial chromosome as a prophage and is replicated with the host, sometimes giving the host new properties; stress can trigger a shift to the lytic cycle.

Ecologically, phages regulate bacterial communities and drive horizontal gene transfer by transduction. They are highly specific for their bacterial hosts, which allows targeted applications but complicates broad-spectrum use.

Applications include phage therapy to combat antibiotic-resistant infections, phage display and phage typing for research and diagnostics, and biocontrol in food safety and agriculture. Regulatory oversight and safety considerations include risks of bacterial resistance, movement of undesirable genes, and ecological impact. Ongoing research seeks to expand therapeutic options and clarify phage–bacteria interactions.