E. Coli Competence
E. Coli Competence - Related Videos
01:28
Training and Competency in Animal Procedures
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2026
All animal procedures described here must be conducted in accordance with institutional animal ethics guidelines and approved by IACUC. All procedures must follow the principles of the 3Rs—Replacement, Reduction, and Refinement—and must be performed by trained personnel. A Stepwise Approach to Training Proper training and competency in animal procedures are essential to ensure high standards of animal welfare and reliable scientific outcomes. A structured, progressive training approach is...
07:46
Transformation of Plasmid DNA into E. coli Using the Heat Shock Method
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Cited by 433 •
2007
Transformation of plasmid DNA into E. coli using the heat shock method is a basic technique of molecular biology. It consists of inserting a foreign ...
07:10
Rapid Protocol for Preparation of Electrocompetent Escherichia coli and Vibrio cholerae
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Cited by 59 •
2013
Electroporation is a commonly employed method for introducing DNA into bacteria in a process known as transformation. Traditional protocols for the preparation of electrocompetent cells are time consuming and labor intensive. This article describes an alternate, rapid, and efficient method for the preparation of electrocompetent cells presently employed by some laboratories.
12:48
The Multifaceted Benefits of Protein Co-expression in Escherichia coli
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Cited by 4 •
2015
Protein co-expression is a powerful alternative to the reconstitution in vitro of protein complexes, and is of help in performing biochemical and genetic tests in vivo. Here we report on the use of protein co-expression in Escherichia coli to obtain protein complexes, and to tune the mutation frequency of cells.
03:13
Competence-Induced DNA Uptake in Staphylococcus aureus
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2025
Source: Cafini, F., et.al. Methodology for the Study of Horizontal Gene Transfer in Staphylococcus aureus. J. Vis. Exp. (2017)This video demonstrates competence-induced DNA uptake in Staphylococcus aureus through natural transformation. A chloramphenicol-sensitive strain engineered to constitutively express a sigma factor is cultured under nutrient-limiting conditions to enhance competence, then incubated with donor DNA carrying a resistance gene. Successful gene transfer is confirmed by the...
FAQs
Chilled divalent cations, such as calcium ions, reduce the electrostatic repulsion between negatively charged DNA and the bacterial cell envelope. This closer association creates conditions in which a brief heat-shock step can promote DNA entry. The result depends on preparing cells under suitable conditions rather than adding calcium ions alone.
The two approaches create DNA-entry conditions through different physical mechanisms. Chemical transformation uses chilled divalent cations followed by brief heat shock, whereas electroporation applies a short electric pulse that creates transient membrane pores. This distinction gives researchers two delivery strategies, with performance influenced by strain, cell preparation, DNA quality, and conditions.
Transformation efficiency depends on several linked variables: the bacterial strain, how cells are prepared, the quality of the DNA, and the conditions used for delivery. Consequently, successful plasmid introduction cannot be attributed to the DNA construct alone. Comparing these factors helps researchers interpret differences in the number of recombinant colonies obtained.
A basic workflow requires bacterial cells, foreign DNA, chilled divalent cations such as calcium ions, and a brief heat-shock step. The cation treatment addresses DNA-cell repulsion, while heat shock promotes entry. Keeping the cations chilled is part of the stated preparation conditions and distinguishes this approach from electric-pulse delivery.
An electroporation workflow contributes a distinct route for introducing plasmid or other foreign DNA: a short electric pulse creates transient pores in the cell membrane, allowing DNA entry. It is therefore useful when researchers want to use electrical delivery rather than cation treatment and heat shock within transformation experiments.
After DNA has been introduced, researchers can use the cells for gene cloning, protein expression, or mutation analysis. Selection then identifies recombinant colonies, making the transformation outcome experimentally useful rather than merely demonstrating DNA entry. The same system therefore supports both construction of DNA molecules and investigation of sequence changes through molecular biology experiments.