Timelines: 1915
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A glassy transformation
Bacteriophages attached to a bacteria cell
Bacteriophage
The lowly bacteriophage — a virus that infects bacteria — makes its entrance on the stage of 20th century genetics research. It will soon steal the show. In 1915, British physician Frederick Twort notices a “glassy transformation” in bacterial colonies growing in his laboratory. He observes that the condition consistently precedes the destruction of cultures. Twort hypothesizes the presence of an invisible parasitic virus. In 1917, at the Pasteur Institut in Paris, French Canadian microbiologist Félix d’Hérelle notes the same phenomenon, draws the same conclusion, and designs a series of experiments to demonstrate that the antibacterial factor can be isolated and transferred. He names the suspected virus bacteriophage. The prospect of developing a viral medicine to combat infectious diseases subsequently draws a large platoon of biomedical researchers to the study of bacteriophage. No therapeutic applications are forthcoming, but the familiarity that biochemists and molecular biologists gain with the organism eventually pays huge dividends in the form of advances in molecular genetics. Bacteriophage becomes a standard experimental model in biological research. Much of what scientists learn about the transcription and translation of DNA in the 1950s and 1960s is derived from bacteriophage studies, and the first genome to be fully sequenced — by Fred Sanger in 1977 — is the single-stranded, ten gene code of the Φ-X 174 bacteriophage that attacks E. coli.
Frederick Twort
Félix d’Hérelle
(left) An electron micrograph of a bacteriophage and (right) a diagram of bacteriophage structure.