title: Studies on transformation of Escherichia coli with plasmids.
abstract: Factors that affect the probability of genetic transformation of Escherichia coli by plasmids have been evaluated. A set of conditions is described under which about one in every 400 plasmid molecules produces a transformed cell. These conditions include cell growth in medium containing elevated levels of Mg2+, and incubation of the cells at 0 degrees C in a solution of Mn2+, Ca2+, Rb+ or K+, dimethyl sulfoxide, dithiothreitol, and hexamine cobalt (III). Transformation efficiency declines linearly with increasing plasmid size. Relaxed and supercoiled plasmids transform with similar probabilities. Non-transforming DNAs compete consistent with mass. No significant variation is observed between competing DNAs of different source, complexity, length or form. Competition with both transforming and non-transforming plasmids indicates that each cell is capable of taking up many DNA molecules, and that the establishment of a transformation event is neither helped nor hindered significantly by the presence of multiple plasmids.
mesh_terms: D002412:Cations; D004278:DNA, Superhelical; D004121:Dimethyl Sulfoxide / Q000494:pharmacology; D004229:Dithiothreitol / Q000494:pharmacology; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics* / Q000254:growth & development; D010957:Plasmids / Q000187:drug effects; D013045:Species Specificity; D014169:Transformation, Bacterial / Q000187:drug effects
chemical_list: D002412:Cations; D004278:DNA, Superhelical; D004229:Dithiothreitol; D004121:Dimethyl Sulfoxide