OriC plasmids do not affect timing of chromosome replication in Escherichia coli K12.
The variability of the time interval between successive rounds of chromosome replication was estimated by density-shift experiments, by measuring the conversion of heavy DNA to hybrid density and light DNAs upon transfer of a steady-state culture growing in medium with [13C]glucose and 15NH4Cl to medium with light isotopes. The coefficient of variation (CV%) for the interreplication time of the Escherichia coli K12 chromosome was found to be 17%, i.e. similar to that for interdivision time. The presence of additional copies of oriC in the cell on a high copy number plasmid did not increase the CV of interreplication time. It is concluded that a single rate-limiting event is unlikely to time the initiation of chromosome replication. The regulation of initiation at oriC and the coordination with cell division is discussed.
Koppes
L J
LJ
Department of Microbiology, University of Uppsala, Sweden.
D002876:Chromosomes, Bacterial / Q000502:physiology*; D004261:DNA Replication; D004269:DNA, Bacterial / Q000032:analysis; D004926:Escherichia coli / Q000235:genetics* / Q000254:growth & development; D007700:Kinetics; D008433:Mathematics; D008957:Models, Genetic; D010957:Plasmids
D004269:DNA, Bacterial