Bacteriophage

Bacteriophage (also known as phages) are viruses that target and infect only bacterial cells. The first observation of what since turned out to be bacteriophage was made in 1896. Almost twenty years later, the British bacteriologist Frederick Twort demonstrated that an unknown microorganism that could pass through a filter that excluded bacteria was capable of destroying bacteria. He did not explore this finding in detail, however. In 1915, the French Canadian microbiologist Felix d'Herelle observed the same result, and named the microorganism bacteriophage (bacteria eater, from the Greek phago, meaning to eat).

Many types of bacteriophage have been identified since their discovery in 1915, and they are named according to the type of bacteria they infect. For example, staphylophages are specific viruses of the staphylococcal bacteria, and coliphages specifically infect coliform bacteria.

Bacteriophage are the most thoroughly studied and well-understood viruses. They occur frequently in nature, carry out similar biological functions as other viruses, yet do not target human cells for infection. Phages have proven to be a valuable scientific research tool for a variety of applications: as models for the study of viral infectious mechanisms, as tools of biotechnology that introduce new genes into bacterial cells, and as potential treatments for human bacterial infection. For example, the experiments that lead to the discovery of messenger Colored transmission electron micrograph of a T4 bacteriophage virus. © Department of Microbiology, Biozentrum/Science Photo Library/Photo Researchers, Inc. ribonucleic acid, one of the keys to the manufacture of protein in bacteria, viruses, and even cells found in humans, were accomplished using a bacteriophage. Another example is the bacteriophage designated T4, which specifically infects the bacterium Escherichia coli. T4 has been a cornerstone of molecular biology; studies of the way T4 makes new copies of itself has revealed a great deal of information about bacteriophage genetics and the regulation of the expression the gene viral genetic material. Additionally, another bacteriophage, called lambda, has been fundamentally important to molecular biology as a model system for gene regulation and as a means of moving genetic material from one bacterium to another.