Bacteriophage DNA recombination. Molecular model showing DNA manipulation and recombination taking place at a Holliday junction with a bacteriophage enzyme. DNA is multicoloured, while the lambda-int integrase protein from a lambda bacteriophage is beige. This complex forms a Holliday junction where the genetic material is excised or integrated into the host chromosome. Bacteriophages are viruses that infect bacteria. The lambda bacteriophage infects enterobacteria.