Plasmid copy number determination

Plasmid copy number is known to vary depending on origin of replication and culture conditions [refs]. Typically, plasmids are referred to in qualitative terms such as "High" "Low" "Single" copy yet the quantitative value can be altered with only slight/single bp changes in the origin of replication [refs] and dramatically alter both the per cell and population yield of other products coded on the plasmid [refs]. Here we describe 3 methods used in our lab and discuss advantages and disadvantages of each.

%warn% note, this page is in progress, and requires additional information .

Overview

Regardless of what method of is used to evaluate the plasmid copy number, all methods are limited by the DNA extraction, and biological relevance of the sample when the DNA is extracted.

To minimize bias in DNA extraction we recommend: never using a "plasmid prep" kit as these kits strongly favor isolation of plasmid DNA over genomic DNA, more?

To maximize biological relevance we recommend isolating DNA under the same conditions as you are interested in or expect there to be a difference (stationary vs exponential growth; media choice; )

Comparison of methods

in progress

-- Main.DanielDeatherage - 11 Oct 2020