pMS76, a plasmid capable of amplification by treatment with chloramphenicol.

pMS76 is a nonconjugative, 5.54-megadalton plasmid. This plasmid is present in Escherichia coli K12 cells at about 20 copies per chromosome. In addition, the pMS76 plasmid can be mobilized by conjugative plasmids and it shares a number of other properties with the amplifiable ColE1 plasmid, including the ability to amplify copy number in the presence of chloramphenicol. However, pMS76 is compatible with ColE1-like replicons, pBR313, and with other multicopy plasmids, RSF1030 and pACYC184. Also the replication of pMS76 is rifampicin sensitive and requires DNA polymerase 1.