Bacteriophage infecting E. coli bacterium. 3D computer illustration of a T4 bacteriophage virus before (attachment position, left) and during (injecting position, right) injecting a DNA (deoxyribonucleic acid) strand into an Escherichia coli bacteria cell. A bacteriophage, or phage, is a virus that infects bacteria. Enterobacteria T4 infects E. coli bacteria. It consists of an icosahedral (20-sided) head, which contains the genetic material, a tail (cylinder) and tail fibres (leg-like). The tail fibres attach to the surface of the bacterium and the tail injects the genetic material into the cell. The viral genetic material then hijacks the bacterium's own cellular machinery, forcing it to produce more copies of the bacteriophage. When a sufficient number