It is known that E.Coli chromosomes, in an ideal growth condition, replicate themselves in about 40min (Cooper et al. 1968). Does anyone know if there are any studies that quantified the rate of replication of ColE1 plasmids?
Has there ever been records of overlapping rounds of replication, similar to the bacterial chromosome, for ColE1?
Cheers
Dear Melchior,
ColE1 is moderate-copy number plasmid, 20-30 copies in E.coli cells grown at 37°C. Its replication rate during elongation step is similar to that for chromosomal replication, about 1000-1200 bp/min, as this is the cellular machinery that provides synthesis of both DNA strands. However, ColE1 replication is under dual control by RNA I (a 108 nt antisense RNA encoded by the plasmid) and Rop (a plasmid protein stabilizing RNA-RNA duplex), which determine the plasmid DNA yield. The deletion of the gene rom (encoding Rom) was shown to be important at preventing runaway replication at slow growth rates. High temperature (> 42 °C) decreases the stability of RNAI/RNAII duplex and thereby, results in increase of copy number. ColE1 amplification could reach up to 1500 copies in the presence of chloramphenicol in a growth medium. A 6-kb ColE1 was used for construction of multi-copy cloning vectors, the best known is pBR322.
Thus, several copies of Col1 could be simultaneously and faster produced (overlapping rounds) in cells independently on chromosomal replication.
This short review should be interesting for you:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2846101/pdf/nihms183157.pdf
Thank you both for directing me to the aforementioned paper. It is indeed exactly what I was looking for. As far as I understand it, ColE1 plasmid replication should take around 3 seconds to complete (tetha type replication) if we base ourselves on DNA polymerase speed. Because of the size of the plasmid and the speed of replication, I guess it would be difficult to experience overlapping rounds of replication. Thank you again
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