A century of the phage: past, present and future

Phages were discovered 100 years ago, and since then phage research has transformed fundamental and translational biosciences. In this Timeline, Salmond and Fineran discuss a century of phage research, describing the roles of phages in ecosystems and in driving bacterial evolution and virulence, and highlight their impact as a source of novel reagents that revolutionized molecular biology and biotechnology. Viruses that infect bacteria (bacteriophages; also known as phages) were discovered 100 years ago. Since then, phage research has transformed fundamental and translational biosciences. For example, phages were crucial in establishing the central dogma of molecular biology — information is sequentially passed from DNA to RNA to proteins — and they have been shown to have major roles in ecosystems, and help drive bacterial evolution and virulence. Furthermore, phage research has provided many techniques and reagents that underpin modern biology — from sequencing and genome engineering to the recent discovery and exploitation of CRISPR–Cas phage resistance systems. In this Timeline, we discuss a century of phage research and its impact on basic and applied biology.