Hanahan D
J Mol Biol. 1983 Jun 5;166(4):557-80. doi: 10.1016/s0022-2836(83)80284-8.
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.
已对影响大肠杆菌被质粒遗传转化概率的因素进行了评估。描述了一组条件，在这些条件下，每400个质粒分子中约有一个能产生一个转化细胞。这些条件包括在含有高水平Mg2+的培养基中进行细胞生长，以及将细胞在0摄氏度下于含有Mn2+、Ca2+、Rb+或K+、二甲基亚砜、二硫苏糖醇和六胺钴（III）的溶液中孵育。转化效率随质粒大小增加而呈线性下降。松弛型和超螺旋型质粒以相似的概率进行转化。非转化DNA的竞争与质量一致。在不同来源、复杂度、长度或形式的竞争DNA之间未观察到显著差异。与转化型和非转化型质粒的竞争表明，每个细胞都能够摄取许多DNA分子，并且多个质粒的存在对转化事件的发生既没有显著促进作用也没有显著阻碍作用。
