TRANSFORMATION AND EXPRESSION OF A STAPHYLOCOCCAL PLASMID IN ESCHERICHIA-COLI

A multiple antibiotic-resistant Staphvlococcus aureus, was found to po ssess three plasmid bands in agarose gel electrophoresis. A plasmid of approximately 4.3 kb (pMC790/2) was found to code for ampicillin and tetracycline resistance and to have one EcoRI site when transformed in to S. aureus RN 4220. pMC790/2 in unmodified form was transformed into a recA- E. coli at a frequency of 1.2 X 10(4) transformants/mug of pl asmid DNA. Plasmid (pMC790/2) replicated, maintained itself stably and expressed far better in the E. coli host than in S. aureus.