The relationship between molecular structure and transformation efficiency of some S. aureus plasmids isolated from B. subtilis.

DNA preparations of the chloramphenicol resistance determining S. aureus plasmids pC194, pC223, and PUB112 can be fractionated by gel electrophoresis into various bands. Electronmicroscopic investigations of these various molecular species obtained with pC194 indicated that, depending on the preparations, 70 to 80% of the molecules were monomers, while the rest consisted of various classes of concatemeric and/or interlocked multimers. Measurements of the specific transforming activity of the various molecular classes indicated that the monomers had less than one thousandth the activity of the multimeric plasmic DNA. pC194 DNA of high specific transforming activity could also be obtained by ligation of HindIII generated monomers into concatemeric DNA.