Bacteriophage

Bacteriophage (pronunciation: /ˈbaktɪərɪəˌfeɪdʒ/), often referred to as phage (pronunciation: /feɪdʒ/), is a type of virus that infects and replicates within bacteria and archaea. The term "bacteriophage" is derived from "bacteria" and the Greek: φαγεῖν (phagein), meaning "to devour".

Bacteriophages are composed of proteins that encapsulate a DNA or RNA genome, and may have relatively simple or elaborate structures. Their genomes may encode as few as four genes, and as many as hundreds of genes. Phages replicate within the bacterium following the injection of their genome into its cytoplasm.

Types of Bacteriophages

There are many types of bacteriophages, which can be classified into one of two life cycles - lytic or lysogenic.

Lytic Bacteriophages - These bacteriophages take over the machinery of the cell to make phage components. They then destroy, or lyse, the cell, releasing new phage particles.
Lysogenic Bacteriophages - These bacteriophages incorporate their nucleic acid into the chromosome of the host cell and replicate with it as part of the cell's DNA.

Applications of Bacteriophages

Bacteriophages have been used for over a century as an alternative to antibiotics in the former Soviet Union and Central Europe, as well as in France. They are seen as a possible therapy against multi-drug-resistant strains of many bacteria.