Plasmid Transformation
Plasmid Transformation - Related Videos
07:46
Transformation of Plasmid DNA into E. coli Using the Heat Shock Method
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Cited by 448 •
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 ...
08:16
Plasmid Purification
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2023
Plasmid purification is a technique used to isolate and purify plasmid DNA from genomic DNA, proteins, ribosomes, and the bacterial cell wall. A plasmid is a small, circular, double-stranded DNA that is used as a carrier of specific DNA molecules. When introduced into a host organism via transformation, a plasmid will be replicated, creating numerous copies of the DNA fragment under study. In this video, a step-by-step generalized procedure is described for how to perform plasmid purification.
04:33
Bacterial Transformation - Concepts
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2019
Background In early 20th century, pneumonia was accountable for a large portion of infectious disease deaths1. In order to develop an effective vaccine against pneumonia, Frederick Griffith set out to study two different strains of the Streptococcus pneumoniae: a non-virulent strain with a rough appearance (R-strain) and a virulent strain with a smooth appearance (S-strain) due to an outer polysaccharide capsule2. This outer layer of the S-strain bacteria enabled them to withstand the host...
05:21
Bacterial Transformation - Student Protocol
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2019
Bacterial Transformation ExpandIMPORTANT: In addition to wearing the appropriate personal protective equipment, be sure to take care to keep your face away from suspension cultures, and to avoid inhaling reagents. Do not touch your face while performing the experiment. Always wash your hands before and after every experiment. When you are ready to safely begin, check to make sure you have a tube or tubes of competent E. coli cells in your ice bucket. Then, transfer 50 µL from one of these tubes...
07:11
Homemade Site Directed Mutagenesis of Whole Plasmids
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Cited by 92 •
2009
Site directed mutagenesis of whole plasmids is a simple way to create slightly different variations of an original plasmid. Here we demonstrate an easy and cost effective way to introduce base substitutions into a plasmid using standard reagents.
FAQs
Both approaches temporarily increase bacterial membrane permeability, but they do so under different conditions. Heat shock is applied to chemically competent cells, whereas electroporation uses an electrical pulse with electrocompetent cells. This transient change allows plasmid DNA to cross the membrane before the cells recover, making the choice of method dependent on the available competent-cell type and transformation workflow.
Success depends on several linked variables: the plasmid must have an appropriate design, the bacterial cells must be sufficiently competent, and the DNA must be suitable in quality. Selection conditions also need to match the construct and the transformed cells. A weakness in any of these areas can reduce recovery of bacteria carrying the desired plasmid.
Selective media helps distinguish cells that acquired the plasmid from cells that did not. When the plasmid provides a matching antibiotic-resistance feature, growth on antibiotic-containing medium enriches for bacteria carrying the construct. This step does not itself prove that every recovered colony has the intended sequence, but it supports isolation of candidate transformants for subsequent research.
A typical workflow begins by combining the plasmid with either chemically competent or electrocompetent bacterial cells. Researchers then use heat shock or an electrical pulse to facilitate DNA entry, allow the cells to recover, and grow them on selective media. Colonies that survive the selection can be isolated as bacterial populations carrying the desired construct.
The method is useful when investigators need bacteria to propagate a selected DNA construct, express a gene, or support a functional study. It can therefore serve gene-cloning projects, recombinant protein production, and experiments examining gene function. The intended application influences which plasmid design and selection conditions are appropriate for recovering useful transformants.
Growth on the appropriate selective medium indicates that bacterial cells likely acquired a plasmid-associated selectable feature, allowing researchers to isolate candidate colonies. Those colonies provide a starting population for work with the construct, including propagation, gene expression, or functional studies. Interpretation depends on maintaining suitable selection conditions and using a plasmid design aligned with the experiment.