Transmission electron microscope of T-Even Bacteriophage particles showing polyhedral heads, helical tails and base plates. Bacteriophages are viruses that infect only bacteria. After attachment to the host's surface, viruses inject their complement of RNA or DNA. The host's DNA is instructed to code for bacteriophage replication and within 20 minutes, the progeny is synthesized and wrapped in a protein coat. Negatively-stained particles at a magnification of 165,00x @ 5x7(inches).