Chitosan Inhibits pBR322 Transformation in Escherichia coli DH5α

09/05/2015

Chongmyung Kim, Nur Ridzwan Nur Saidy, Rebecca Fu, Rui Wang

Department of Microbiology and Immunology, University of British Columbia

Volume 19
Fall 2014 / Winter 2015

The effect of chitosan, a polycationic biopolymer, during transformation in Gram-negative Escherichia coli DH5α cells was investigated in this study. Chitosan was hypothesized to enhance transformation efficiency by transient membrane permeabilization in E. coli DH5α cells through electrostatic interactions. Transformation efficiency of chitosan-mediated transformation was compared to the conventional heat shock method and the optimal conditions to use chitosan were determined by performing a pH assay, minimum-inhibitory concentration assay, and DNA optimization assay. In comparison to the heat shock method, chitosan-supplemented transformation did not enhance bacterial transformation in E. coli DH5α cells. Furthermore, chitosan-supplementation in heat shock transformation resulted in a decrease in transformation efficiency. The effect of chitosan on cell growth was further investigated and cell aggregates were observed in chitosan-treated E. coli DH5α cells in addition to reduced cell growth. Results from this study showed that chitosan inhibits transformation in Gram-negative E. coli DH5α cells in comparison to the heat shock method of bacterial transformation. The mechanism of inhibition may be due to the formation of a cell-chitosan complex that physically excluded DNA, resulting in decreased transformation efficiency.