Related Experiment Videos
Natural plasmid transformation in Escherichia coli
Suh-Der Tsen1, Suh-Sen Fang, Mei-Jye Chen
1Department of Microbiology, Graduate Institute of Microbiology and Immunology, National Yang-Ming University, Taipei, Taiwan, ROC. nymutsen@ym.edu.tw
Journal of Biomedical Science
|June 18, 2002
Summary
Escherichia coli can naturally take up plasmids, a process enhanced by specific methods. This natural plasmid transformation in E. coli is recA-independent and occurs most efficiently with supercoiled DNA.
Area of Science:
- Microbiology
- Molecular Biology
- Bacterial Genetics
Background:
- Escherichia coli is a model organism lacking a known natural transformation process.
- Extracellular plasmid uptake by E. coli occurs at low frequencies naturally.
- Understanding natural transformation mechanisms is crucial for genetic engineering and microbial research.
Purpose of the Study:
- To investigate and characterize the natural plasmid transformation process in Escherichia coli.
- To identify factors influencing the efficiency of natural transformation.
- To determine if a specific DNA sequence is recognized during natural plasmid uptake.
Main Methods:
- Development of a standard method involving stationary phase cell concentration, plasmid mixing, and selective plating.
- Assessment of competence development during different growth phases (lag and exponential).
- Evaluation of DNA forms (supercoiled, linear concatemeric, linear monomeric) for transformation efficiency.
- RecA-independence and conjugation-independence assays.
- Plasmid modification by inserting DNA fragments and random oligonucleotides.
Main Results:
- Natural plasmid transformation in E. coli was observed and characterized.
- Competence for transformation was highest during the lag phase and decreased during exponential growth.
- Supercoiled monomeric and linear concatemeric DNA efficiently transformed cells, while linear monomeric DNA did not.
- Transformation efficiency increased with plasmid concentration up to a plateau.
- Most E. coli strains exhibited this natural transformation process.
- Plasmid pACYC184 became transformable after insertion of an ampicillin resistance gene.
- A specific recognition sequence, resembling E. coli's bacterial interspersed medium repetitive sequence, was identified.
Conclusions:
- Plasmid natural transformation is a viable process in Escherichia coli.
- The process is recA-independent and not related to conjugation.
- Specific DNA sequences may be recognized for efficient uptake during natural transformation.