Bacteriophage- Definition, Structure, Life Cycles, Applications, Phage Therapy


Bacteriophages, or phages for short, are viruses that infect and replicate within bacteria and archaea . They are the natural enemies of bacteria and help keep bacterial growth in check in nature. They are also the most abundant and diverse biological entities on Earth, with an estimated 10^31^ phage particles in existence.

Bacteriophages were discovered independently by Frederick W. Twort in Great Britain (1915) and Félix d’Hérelle in France (1917) . D’Hérelle coined the term bacteriophage, meaning “bacteria eater,” to describe the agent’s bacteriocidal ability. He also pioneered the use of phages as therapeutic agents against bacterial infections, a practice known as phage therapy.

Bacteriophages have a simple structure that consists of a core of genetic material (DNA or RNA) surrounded by a protein capsid . Some phages also have a tail and tail fibers that help them attach to specific receptors on the surface of bacterial cells . Phages vary greatly in their size, shape, genome organization, and host range. They are classified into different orders and families based on their morphology and genetic material.

Bacteriophages have two main modes of reproduction: lytic and lysogenic . In the lytic mode, the phage injects its genome into the bacterial cell and takes over its machinery to produce new phage particles. The phage then lyses (breaks) the cell and releases the progeny phages. In the lysogenic mode, the phage integrates its genome into the bacterial chromosome and becomes dormant. The phage genome, called a prophage, is copied along with the bacterial DNA during cell division. Under certain conditions, the prophage can be activated and switch to the lytic mode.

Bacteriophages have many applications in science, medicine, agriculture, and industry . They are used as tools for molecular biology, genetics, biochemistry, and biotechnology. They are also used as biocontrol agents against bacterial pathogens in humans, animals, plants, and food products. They offer advantages over antibiotics such as specificity, safety, diversity, and adaptability. However, they also face challenges such as resistance, regulation, standardization, and public acceptance.

Bacteriophages are fascinating viruses that have shaped the evolution of bacteria and influenced the ecology of life on Earth. They are also promising candidates for developing novel strategies to combat bacterial infections and improve human health.