Bacterial transformation

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Transformation is the process of introducing foreign DNA (e.g plasmids, BAC) into a bacterium. Bacterial cells into which foreign DNA can be transformed are called "competent". Some bacteria are naturally competent (e.g B. subtilis), whereas others such as E. coli are not naturally competent. Non-competent cells can be made competent and then transformed via one of two main approaches; chemical transformation and electroporation.

There are advantages and disadvantages to both transformation methods. In general, chemical transformation is less prone to error and faster however electroporation produces a higher transformation efficiency (fraction of transformed cells that actually uptake the foreign DNA). See Molecular Cloning for a fuller discussion of both approaches.


OpenWetWare already has a number of protocols relating to bacterial transformation but more are always welcome. If you plan on doing a chemical transformation, then you should see these pages -

If you plan on using electroporation, then see these pages -

If you use a variant on one of these protocols please feel free to add a link to your protocol from one of these pages so other users can find a protocol that works for them. Additionally, if anyone uses the Innoe or Hanahan high-efficiency protocols, then please add protocols here.

Chemical transformation buffer comparison



  1. ISBN:0-87969-577-3 [MolecularCloning]

Online version

  1. Hanahan D, Jessee J, and Bloom FR. Plasmid transformation of Escherichia coli and other bacteria. Methods Enzymol. 1991;204:63-113. PubMed ID:1943786 | HubMed [Hanahan91]
  2. US Patent 4,851,348 Media:pat4851348.pdf [Hanahan89]
  3. US Patent 4,981,797 Media:pat4981797.pdf [Jessee90]
  4. US Patent 6,247,369 Media:pat6274369.pdf [Donahue01]
  5. US Patent 6,706,525 Media:pat6706525.pdf [Greenr04]
  6. US Patent 6,709,854 Media:pat6709854.pdf [Donahue04]
  7. US Patent 6,855,494 Media:pat6855494.pdf [Bloom05]
  8. US Patent 6,960,464 Media:pat6960464.pdf [Jessee05]