Datta A, Parker C D, Wohlhieter J A, Baron L S
J Bacteriol. 1973 Feb;113(2):763-71. doi: 10.1128/jb.113.2.763-771.1973.
Vibrio cholerae strains with the transmissible fertility factor P contained a supercoiled circular deoxyribonucleic acid (DNA) component amounting to between 2 and 6% of the total DNA obtained from the cells. Such a component was not observed in V. cholerae strains lacking the fertility factor. This supercoiled circular DNA was isolated from P(+) cells, and the molecular weight was determined by sedimentation velocity experiments and electron microscopy to be approximately 80 million daltons. These supercoiled circular DNA molecules, which have a guanine plus cytosine (G + C) composition of 42%, were concluded to be the extrachromosomal P factor. It was calculated that there is approximately one copy of the P factor per chromosome. A small amount of supercoiled circular DNA was occasionally isolated from the P(-) strains of V. cholerae. The function of this component, which has a molecular weight of 40 million daltons, is not known. The molecules found in the P(-) strains were readily distinguished from the P(+) circular molecules by their smaller molecular weight and different G + C composition.
带有可传递致育因子P的霍乱弧菌菌株含有一种超螺旋环状脱氧核糖核酸（DNA）成分，其占从细胞中获得的总DNA的2%至6%。在缺乏致育因子的霍乱弧菌菌株中未观察到这种成分。这种超螺旋环状DNA是从P（+）细胞中分离出来的，通过沉降速度实验和电子显微镜测定其分子量约为8000万道尔顿。这些超螺旋环状DNA分子的鸟嘌呤加胞嘧啶（G + C）组成为42%，被认为是染色体外的P因子。据计算，每条染色体大约有一个P因子拷贝。偶尔会从霍乱弧菌的P（-）菌株中分离出少量超螺旋环状DNA。这种分子量为4000万道尔顿的成分的功能尚不清楚。在P（-）菌株中发现的分子通过其较小的分子量和不同的G + C组成很容易与P（+）环状分子区分开来。
