Common bacteriophage include T7 and Lamda phage. Lytic phages are more suitable for phage therapy. The packaging of bacteriophage DNA into phage capsids has low fidelity. The phage antibody libraries are a variant of phage antigen libraries. The invention of antibody phage display revolutionised antibody drug discovery. Viral protein interactomes consist of interactions among viral or phage proteins. Part of the phage genome was nonessential and possibly bacterial. DNA sequences are originally from the lambda phage. The virion is similar in structure to the T4 phage but simpler. Reports suggest this bacterium is susceptible to phage therapy. Basepairing between the PAM and the phage genome is required in type II systems. Bacteria can reduce their susceptibility by changing their surface receptors and thus preventing phage adsorption. Two successful approaches have been identified&colon; transgenic mice and phage display. Another way for bacteria to defend against phage infection is by having chromosomal islands. New spacers can appear rapidly as part of the immune response to phage infection.