Construction and characterization of new coliphage M13 cloning vectors

New single-stranded DNA cloning vectors have been constructed by the insertion of additional DNA fragments into a HaeII restriction site in the bacteriophage M13 duplex replicative form (RF). These inserts into the M13 genome bring a single restriction sites useful for cloning, including PstI, XorII, EcoRI, SstI, XhoI, KpnI, and PvuII. Drug-resistance genes cloned into M13 include the beta-lactamase (bla) gene and the chloramphenicol acetyl transferase (cat) gene. These vectors provide a convenient means of easily obtaining the separated strands of a cloned duplex DNA fragment by cloning the fragment in each of the two possible orientations. Standard cloning techniques commonly applied to double-stranded DNAs can be utilized to insert foreign DNAs into the duplex RF DNAs of these vectors. Cells transformed by chimeric DNAs extrude filamentous phage particles carrying a circular single-stranded copy of the chimeric viral strand. Because M13-infected cells continue to grow and divide, cells can be transformed to yield either plaques or drug-resistant colonies. Specific inserts are readily detected by plaque hybridization techniques using an appropriate probe. Chimeric viral single strands from virus particles in the supernatant of small volumes of infected cultures can be rapidly and sensitively analyzed by agarose gel electrophoresis to determine the size of an insert.