Color enhanced Tramnsmission Electron Microscope (TEM) of DNA from a lambda wild type bacteriophage. Enterobacteria phage (lambda phage, coliphage) is a bacterial virus, or bacteriophage, that infects the bacterial species Escherichia coli (E. coli). The wild type of this virus has a temperate lifecycle that allows it to either reside within the genome of its host through lysogeny or enter into a lytic phase (during which it kills and lyses the cell to produce offspring); mutant strains are unable to lysogenize cells- instead they grow and enter the lytic cycle after superinfecting an already lysogenized cell. The phage particle consists of a head (capsid), a tail, and tail fibers. The head contains the phage's double-strand linear DNA genome. During infection, the phage particle recognizes and binds to its host, E. coli, causing DNA in the head of the phage to be ejected through the tail into the cytoplasm of the bacterial cell. Magnification: 20,000x at 35 mm size.