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Eclipse period duri...
Eclipse period during replication of plasmid R1 : Contributions from Structural events and from Copy-Number-control system
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- Olsson, Jan (author)
- Uppsala universitet,Institutionen för cell- och molekylärbiologi
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- Berg, Otto G. (author)
- Uppsala universitet,Evolutionsbiologi
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- Dasgupta, Santanu (author)
- Uppsala universitet,Institutionen för cell- och molekylärbiologi
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- Nordström, Kurt (author)
- Uppsala universitet,Institutionen för cell- och molekylärbiologi
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(creator_code:org_t)
- 2003-08-18
- 2003
- English.
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In: Molecular Microbiology. - : Wiley. - 0950-382X .- 1365-2958. ; 50:1, s. 291-301
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Abstract
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- 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.
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- art (subject category)
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