The Effects of the Ratio of Surface Area to Volume on Transformation Efficiency in Escherichia coli K-12

Abstract

In the process of transformation, bacteria take up DNA from the environment through their cell wall. To induce competence in the cells, the DNA for uptake must first attach to the cell surface prior to passing through the membrane. Previous studies on the effect of surface area on transformation efficiency have shown decreased transformation efficiencies in large E.coli cells as compared to smaller strains. The reasons remain unknown. We proposed that the surface area to volume ratio (SA:V) to be the determining parameter on transformation efficiency, with a higher ratio leading to higher transformation efficiencies. In order to assess this model, we transformed wild type Escherichia coli (BW25113) and a smaller mutant strain (JW2500) with different amounts of the plasmid vector pUC19.The mutant strain JW2500 with a lower SA:V ratio but a similar surface area to the parent strain displayed 70% ± 5% of the number of transformants from the wild-type strain BW25113. Such results suggest a direct relationship between SA:V ratio and the observed changes in transformation efficiency.