title: Replication of ColE1 plasmid deoxyribonucleic acid in a thermosensitive dnaA mutant of Escherichia coli.
abstract: The replication of ColE1 deoxyribonucleic acid (DNA) took place at the restrictive temperature in a dnaA mutant, dnaA167(Ts). It proceeded at a constant rate at 42 degrees C for at least 3 h. The replication was insensitive to rifampin, which blocked replication at the permissive temperature or in the presence of chloramphenicol, even at the restrictive temperature. A linear DNA strand of ColE1 longer than unit genome size was synthesized. The structure of the replicating molecules observed by electron microscopy was mostly sigma shaped, composed of a circle of a unit genome length with a double-stranded tail. These observations suggest that the replication of ColE1 DNA proceeds via a rolling-circle type of structure in the absence of dnaA function.
mesh_terms: D002499:Centrifugation, Density Gradient; D002701:Chloramphenicol / Q000494:pharmacology; D004261:DNA Replication / Q000187:drug effects; D004269:DNA, Bacterial / Q000096:biosynthesis*; D004926:Escherichia coli / Q000235:genetics* / Q000378:metabolism; D009154:Mutation; D009690:Nucleic Acid Conformation; D010957:Plasmids; D012293:Rifampin / Q000494:pharmacology; D013696:Temperature
chemical_list: D004269:DNA, Bacterial; D002701:Chloramphenicol; D012293:Rifampin