Twort, Frederick William (1877–1950)

English bacteriologist, the original discoverer in 1915 of bacteriophages (often called phages), the relatively large viruses that attack and destroy bacteria. He also researched into Johne's disease, a chronic intestinal infection of cattle.

Twort was born in Camberley, Surrey, and studied medicine at St Thomas's Hospital, London. From 1909 he was superintendent of the Brown Institute, a pathology research centre, and he was also professor of bacteriology at the University of London from 1919.

While working with cultures of Staphylococcus aureus (the bacterium that causes the common boil), Twort noticed that colonies of these bacteria were being destroyed. He isolated the substance that produced this effect and found that it was transmitted indefinitely to subsequent generations of the bacterium. He then suggested that the substance was a virus. Twort was unable to continue this work, and the importance of bacteriophages was not recognized until the 1950s.

Twort also discovered that vitamin K is needed by growing leprosy bacteria, which opened a new field of research into the nutritional requirements of micro-organisms.