Document Detail

Eclipse period of R1 plasmids during downshift from elevated copy number: Nonrandom selection of copies for replication.
MedLine Citation:
PMID:  22293171     Owner:  NLM     Status:  Publisher    
The classical Meselson-Stahl density-shift method was used to study replication of pOU71, a runaway-replication derivative of plasmid R1 in Escherichia coli. The miniplasmid maintained the normal low copy number of R1 during steady growth at 30°C, but as growth temperatures were raised above 34°C, the copy number of the plasmid increased to higher levels, and at 42°C, it replicated without control in a runaway replication mode with lethal consequences for the host. The eclipse periods (minimum time between successive replication of the same DNA) of the plasmid shortened with rising copy numbers at increasing growth temperatures (Olsson et al., 2003). In this work, eclipse periods were measured during downshifts in copy number of pOU71 after it had replicated at 39 and 42°C, resulting in 7- and 50-fold higher than normal plasmid copy number per cell, respectively. Eclipse periods for plasmid replication, measured during copy number downshift, suggested that plasmid R1, normally selected randomly for replication, showed a bias such that a newly replicated DNA had a higher probability of replication compared to the bulk of the R1 population. However, even the unexpected nonrandom replication followed the copy number kinetics such that every generation, the plasmids underwent the normal inherited number of replication, n, independent of the actual number of plasmid copies in a newborn cell.
Jan A Olsson; Otto Berg; Kurt Nordström; Santanu Dasgupta
Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2012-1-20
Journal Detail:
Title:  Plasmid     Volume:  -     ISSN:  1095-9890     ISO Abbreviation:  -     Publication Date:  2012 Jan 
Date Detail:
Created Date:  2012-2-1     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  7802221     Medline TA:  Plasmid     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
Copyright Information:
Copyright © 2012 Elsevier Inc. All rights reserved.
Department of Cell and Molecular Biology, Uppsala University, S-751 24 Uppsala, Sweden.
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