Illustration of a tailspike protein (TSP) from the thermophilic bacteriophage GVE2. Bacteriophages, or phages, are viruses that infect bacteria. Tailspike proteins recognise and bind to the bacterial cell membrane. Once bound, the phage injects it genetic material into the bacterium, where it uses the hosts machinery to replicate itself. When a sufficient number of new phages have been produced, they burst out of the cell, killing it.