Cell-cycle-specific F plasmid replication: regulation by cell size control of initiation.
F plasmid replication during the Escherichia coli division cycle was investigated by using the membrane-elution technique to produce cells labeled at different times during the division cycle and scintillation counting for quantitative analysis of radioactive plasmid DNA. The F plasmid replicated, like the minichromosome, during a restricted portion of the bacterial division cycle; i.e., F plasmid replication is cell-cycle specific. The F plasmid replicated at a different time during the division cycle than a minichromosome present in the same cell. F plasmid replication coincided with doubling in the rate of enzyme synthesis from a plasmid-encoded gene. When the cell cycle age of replication of the F plasmid was determined over a range of growth rates, the cell size at which the F plasmid replicated followed the same rules as did replication of the bacterial chromosome--initiation occurred when a constant mass per origin was achieved--except that the initiation mass per origin for the F plasmid was different from that for the chromosome origin. In contrast, the high-copy mini-R6K plasmid replicated throughout the division cycle.
Keasling
J D
JD
Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor 48109-0620.
Palsson
B O
BO
Cooper
S
S
D002453:Cell Cycle / Q000502:physiology*; D004261:DNA Replication; D004587:Electrophoresis, Agar Gel; D005144:F Factor / Q000502:physiology*; D006801:Humans