Bacteriophages are viruses that parasitize and kill bacteria and hence the name Bacteriophage (bacteria eaters; phagos=to eat). Bacteriophages are highly specific, naturally occurring agents that enter bacteria and destroy them.
There exist two classifications of bacteriophages: lytic and lysogenic. All references to bacteriophages within this website are to lytic bacteriophages (lysogenic bacteriophages are not useful for therapeutic purposes). T4 bacteriophage is an assembly of protein components and DNA. The head is protein membrane, shaped like a kind of prolate icosahedron with 30 facets and filled with deoxyribonucleic acid (DNA). It is attached by a collar (and neck) to a tail consisting of hollow core surrounded by a contractile sheath and based on a spiked end plate to which six fibers are attached.
The spikes and fibers affix the phage to a bacterial cell wall. The sheath contracts, driving the core through the wall, and phage DNA enters the cell.
Bacteriophages are used to cure diseases particularly where antibiotics have proven to be either ineffective or where the disease-causing bacteria have built resistance against the prescribed antibiotics.
A bacteriophage attaches itself, through specific receptors, to the surface of the host bacterial cell and injects its nucleic acid (DNA or RNA) into the bacterium. The bacteriophage DNA redirects the bacterial cell's biosynthetic machinery to produce hundreds of new bacteriophages which, when released, destroy the bacterial cell. The new bacteriophages invade other bacteria in the vicinity and the process is repeated about every thirty minutes until all of the bacteria are eliminated. At this time, the bacteriophages, being non-living entities, self-eliminate because the bacteria that they require as hosts no longer exist.