Eclipse period during replication of plasmid R1: Contributions from Structural events and from Copy-Number-control system
2003 (English)In: Molecular Microbiology, ISSN 0950-382X, E-ISSN 1365-2958, Vol. 50, no 1, 291-301 p.Article in journal (Refereed) Published
The eclipse period (the time period during which a newly replicated plasmid copy is not available for a new replication) of plasmid R1 in Escherichia coli was determined with the classic Meselson-Stahl density-shift experiment. A mini-plasmid with the wild-type R1 replicon and a mutant with a thermo-inducible runaway-replication phenotype were used in this work. The eclipses of the chromosome and of the wild-type plasmid were 0.6 and 0.2 generation times, respectively, at temperatures ranging from 30 degrees C to 42 degrees C. The mutant plasmid had a similar eclipse at temperatures up to 38 degrees C. At 42 degrees C, the plasmid copy number increased rapidly because of the absence of replication control and replication reached a rate of 350-400 plasmid replications per cell and cell generation. During uncontrolled replication, the eclipse was about 3 min compared with 10 min at controlled replication (the wild-type plasmid at 42 degrees C). Hence, the copy-number control system contributed significantly to the eclipse. The eclipse in the absence of copy-number control (3 min) presumably is caused by structural requirements: the covalently closed circular plasmid DNA has to regain the right degree of superhelicity needed for initiation of replication and it takes time to assemble the initiation factors.
Place, publisher, year, edition, pages
2003. Vol. 50, no 1, 291-301 p.
IdentifiersURN: urn:nbn:se:uu:diva-90567DOI: 10.1046/j.1365-2958.2003.03683.xPubMedID: 14507381OAI: oai:DiVA.org:uu-90567DiVA: diva2:162961