Color-enhanced transmission electron micrograph (TEM) of T4 bacteriophages surrounding an Escherichia coli bacterium. Bacteriophages are viruses that infect only bacterium, some being specific to a single species. Having no reproductive machinery, they commandeer the bacteriums to ensure self-replication. They attach themselves to the surface of a bacterium, injecting their complement of DNA or RNA into the host cell. 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. The bacterium, however is usually destroyed by bursting (lysis). Magnification 15,300x at 35mm size.