What are Bacteriophages?

Bacteriophages (Greek for ‘eaters of bacteria’) are also commonly known as phages. They are thought to be the most abundant and diverse life forms on Earth. A lytic phage can rapidly kill a host bacterial cell and in the process, also make copies of itself to attack and kill additional nearby bacterial cells until they have been eliminated.


Phages are about 100 times smaller than bacteria and while they come in different sizes and shapes, many phages share the same basic characteristics.

A phage’s head structure consists of one or more proteins that protectively contain its core genetic material. Many phages also have a tail attached to their heads, which delivers the genetic material once the phage has attached itself to the bacterial host cell. Tail fibers radiate outward from the body to aid in binding to the surface of the target bacteria.


Phages were commonly used as antibacterial therapeutics prior to the advent of antibiotics in 1940. However, antibiotic discovery led to a decline in phage use and research. Phages remain a commonly used antibacterial treatment in Eastern Europe and have been shown to be efficacious, although only anecdotally.