Bacteriophage – Definition, Function & Therapy
Bacteriophages are viruses that exclusively infect and destroy bacteria. They are considered a promising alternative to antibiotics in the treatment of resistant infections.
Wissenswertes über "Bacteriophage"
Bacteriophages are viruses that exclusively infect and destroy bacteria. They are considered a promising alternative to antibiotics in the treatment of resistant infections.
What is a Bacteriophage?
A bacteriophage (or simply phage) is a type of virus that exclusively infects and replicates within bacteria. The name derives from Greek and roughly translates to bacteria eater. Bacteriophages are the most abundant biological entities on Earth and are found in virtually every environment where bacteria exist – including soils, water, and the human body.
Phages are not considered living organisms in the classical sense, as they lack their own metabolism. They consist of a protein shell (capsid) and genetic material (DNA or RNA), and their sole biological function is to enter host bacteria and replicate inside them.
Mechanism of Action
Bacteriophages attach to the surface of bacteria using highly specific receptor-binding proteins. This specificity is a defining feature: each phage typically targets only a specific bacterial strain or a closely related group.
There are two main replication cycles:
- Lytic cycle: The phage injects its genetic material into the bacterium, hijacks the cell machinery to produce new phage copies, and ultimately destroys (lyses) the bacterium upon release. This cycle results in bacterial death.
- Lysogenic cycle: The phage integrates its genetic material into the bacterial genome, where it is replicated passively over multiple generations without immediately killing the host. Under certain conditions, the lytic cycle can be reactivated.
Medical Significance
Phage Therapy
Phage therapy is a medical approach that uses bacteriophages to treat bacterial infections. It was first developed in the early 20th century but fell into disuse with the advent of antibiotics. In light of growing antibiotic resistance, it is now experiencing a scientific revival.
Phage therapy offers several potential advantages:
- Highly targeted action against specific bacteria without disrupting the healthy microbiome
- Effective against multidrug-resistant organisms (e.g., MRSA, resistant Pseudomonas strains)
- Phages can self-replicate at the site of infection, potentially self-regulating their concentration
- Can be combined with antibiotics for synergistic effects
Diagnostic Applications
Phages are also used in laboratory diagnostics to identify specific bacterial strains. A technique known as phage typing exploits the specificity of phages to classify pathogens.
Biotechnological Use
In molecular biology and biotechnology, bacteriophages serve as important research tools. They are used in gene cloning, vaccine development, and cancer research, among other applications.
Current Research and Clinical Relevance
Research into the therapeutic use of bacteriophages is growing worldwide. Multiple clinical trials are investigating the use of phages in hard-to-treat infections, particularly in patients with multidrug-resistant pathogens, chronic wounds, or device-related infections. In some countries – most notably Georgia and Poland – phage therapy is already used in clinical practice.
Ongoing challenges include standardized phage production, regulatory approval pathways, and the potential for bacteria to develop resistance against phages.
References
- Sulakvelidze A., Alavidze Z., Morris J. G. Jr. – Bacteriophage Therapy. Antimicrobial Agents and Chemotherapy, 2001; 45(3): 649–659. PubMed.
- World Health Organization (WHO) – Antimicrobial resistance: global report on surveillance. WHO Press, 2014.
- Gordillo Altamirano F. L., Barr J. J. – Phage Therapy in the Postantibiotic Era. Clinical Microbiology Reviews, 2019; 32(2): e00066-18. PubMed.
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Related search terms: Bacteriophage + Bacteriophages + Phage + Phages