Bacteriophage viruses. Coloured transmission electron micrograph (TEM) of unidentified bacteriophages. Bacteriophages infect one or a few strains of bacteria. Each of those seen here has a many-sided protein head" or capsid (red objects), containing its genetic material. Bacteriophages attach to specific sites on the outside of their host cell and infect it with their genetic material, which enters the cell with or without the capsid. The material instructs the host to produce the molecules necessary for the assembly of new phages. Completed phages are released from the host, often destroying it as they leave. Magnification: x62,500 at 6x6cm size."