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- Title
Cloning of replication origins from the E. coli K12 chromosome.
- Authors
DIAZ, R.; PRITCHARD, R. H.
- Abstract
MINIPLASMIDS, containing only an origin of replication and plasmid-coded functions necessary for plasmid replication and maintenance have been isolated from larger plasmids1. The technique used was to cleave the parent plasmid with the restriction endonuclease EcoRI and reanneal and ligate the fragments so generated in the presence of another EcoRI-generated fragment of DNA coding for a β-lactamase. This second fragment was not capable of self-replication but hybrids between it and a plasmid fragment which was able to replicate could be detected because calls of Escherichia coli transformed with such hybrids would be resistant to ampicillin. We have used the same technique to isolate minichromosomes from the total chromosomal DNA of E. coli K12 and have found that two different chromosomal EcoRI fragments can function as autonomously replicating plasmids. One type of plasmid is indistinguishable from that isolated independently by Yasuda and Hirota2 and contains the origin of replication normally active in chromosome replication termed oriC (refs 3-6). The other type, which we call oriJ plasmids to distinguish them from oriC plasmids, are described below. Both types can be isolated from a single strain of E. coli and they contain chromosomal DNA which is not homologous in DNA · DNA hybridisation studies. Consequently we conclude that the E. coli K12 chromosome contains at least two segments of DNA capable of self-replication.
- Publication
Nature, 1978, Vol 275, Issue 5680, p561
- ISSN
0028-0836
- Publication type
Article
- DOI
10.1038/275561a0