ISSN:
1432-072X
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Summary An Escherichia coli 15 strain has been constructed which contains, in addition to the plasmids inherent to E. coli 15 (P 1-like DNA and minicircular DNA), the colicinogenic factor E1 (Col E1). Whereas the P 1-like DNA of E. coli 15 is unaffected by the uptake of the colicin plasmid, the number of copies of minicircular DNA of E. coli 15 decreases and an equivalent amount of Col E1 DNA becomes established in the cell. The ratio between these two small plasmids is dependent on the growth temperature. The mode of replication of minicircular DNA and Col E1 DNA is very similar, but is different in various respects from that of the P 1-like plasmid: 1. Both small plasmids continue to replicate in the presence of chloramphenicol, whereas the replication of P 1-like DNA stops like the chromosomal DNA. 2. Rifampicin inhibits the synthesis of both small plasmids rather rapidly. The replication of P 1-like DNA continues during the remaining replication cycle of the chromosome in the presence of rifampicin. 3. The replication of Col E1 DNA and of the minicircular DNA still proceeds at elevated temperatures (45–50°C), whereas little or no incorporation of 3H-thymidine into P 1-like DNA is observed at these temperatures. 4. Mutants have been obtained, which show altered properties in the maintenance and replication of the plasmids without being affected in the replication of the chromosomal DNA. In all these mutants the replication and (or) maintenance of the minicircular DNA of E. coli 15 and Col E1 DNA is affected in the same way, but not that of the P 1-like plasmid.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00427929
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