Natural plasmid transformation in Escherichia coli

Suh Der Tsen, Suh Sen Fang, Mei Jye Chen, Jun Yi Chien, Chih Chun Lee, Darwin Han Lin Tsen

Research output: Contribution to journalArticlepeer-review

45 Citations (Scopus)


Although Escherichia coli does not have a natural transformation process, strains of E. coli can incorporate extracellular plasmids into cytoplasm 'naturally' at low frequencies. A standard method was developed in which stationary phase cells were concentrated, mixed with plasmids, and then plated on agar plates with nutrients which allowed cells to grow. Transformed cells could then be selected by harvesting cells and plating again on selective agar plates. Competence developed in the lag phase, but disappeared during exponential growth. As more plasmids were added to the cell suspension, the number of transformants increased, eventually reaching a plateau. Supercoiled monomeric or linear concatemeric DNA could transform cells, while linear monomeric DNA could not. Plasmid transformation was not related to conjugation and was recA-independent. Most of the E. coli strains surveyed had this process. All tested plasmids, except pACYC184, could transform E. coli. Insertion of a DNA fragment containing the ampicillin resistance gene into pACYC184 made the plasmid transformable. By inserting random 20-base-pair oligonucleotides into pACYC184 and selecting for transformable plasmids, a most frequent sequence was identified. This sequence resembled the bacterial interspersed medium repetitive sequence of E. coli, suggesting the existence of a recognition sequence. We conclude that plasmid natural transformation exists in E. coli.

Original languageEnglish
Pages (from-to)246-252
Number of pages7
JournalJournal of Biomedical Science
Issue number3
Publication statusPublished - Jun 26 2002
Externally publishedYes


  • Escherichia coli transformation
  • Natural transformation, plasmid
  • Transformation

ASJC Scopus subject areas

  • Endocrinology, Diabetes and Metabolism
  • Molecular Biology
  • Clinical Biochemistry
  • Cell Biology
  • Biochemistry, medical
  • Pharmacology (medical)


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