Description of Competent Cells

Competence is a special physiological state of a bacterial cell in which a cell can take up exogenous DNA from the surrounding environment and is not easily decomposed by a restriction endonuclease inside the cell.

Using specific techniques in a laboratory setting, bacterial cells can be transformed into the state of competence for molecular biology applications. For example, the electrical method takes advantage of the low-permeability of bacterial cells in their rapidly-growing phase of their life cycle. By shocking bacteria at this stage with high-intensity transient electric field, the negatively-charged DNA passes through the cell membrane and enters the cell.

DIY Protocol for Generating Electro-Competent Cells


  • Bacterial cells
  • LB medium
  • LB agar plates
  • Sterile ddH2O
  • Glycerol (10%)


  • Shaker
  • Stationary and shaking incubator
  • Refrigerated centrifuge
  • Ice bucket with ice and liquid nitrogen
  • Tubes (centrifuge, test, Eppendorf)