Abstract
We adopted epifluorescent microscopy to observe plasmid DNA in situ using Escherichia coli strain EJ812 (parCt8) as the host cell. In this strain abnormal chromosome partition occurs in the restrictive temperature, so that only plasmid DNA exists without chromosome DNA in some cells. EJ812 was transformed by either pBR322 or pUC18. When the transformant cells were incubated for three hours at 42°C, about 30% of them became finally anucleate. When the anucleate cells separeted from the normal cells were stained with 4'6-diamino-2-phenylindole, a few minute granules with fluorescent reaction were observed in the anucleate cells. They are inferred to be the complex of catenated plasmid DNA caused by an effect of parC. One anucleate cell was estimated to contain between 30 and 140 copies of the DNA molecule.
