M13mp18 is the double-stranded, covalently closed, circular form of DNA derived from bacteriophage M13.

This phage vector contains single HindIII, SphI, SbfI, PstI, SalI (AccI/ HincII), XbaI, BamHI, SmaI (XmaI), KpnI (Acc65I), SacI and EcoRI sites within the β-Galactosidase gene. When a fragment of DNA is inserted into one of these sites, the β-Galactosidase gene is inactivated, providing selection for clones on the appropriate indicator plate. DNASU and Addgene are central repositories for plasmid clones and collections that may also be helpful. The phage M13mp18 is propagated in E. coli ER2738. The replicative form of DNA is isolated from infected cells and purified by a standard plasmid purification procedure. The final preparation is tested for its suitability as a vector.