
Figure 1: Schematic representation of transformation in bacteria
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Bacterial transformation is a process of horizontal gene transfer by which some bacteria take up foreign genetic material (naked DNA) from the environment. It was first reported in Streptococcus pneumoniae by Griffith in 1928.1 DNA as the transforming principle was demonstrated by Avery et al in 1944.2
The process of gene transfer by transformation does not require a living donor cell but only requires the presence of persistent DNA in the environment. The prerequisite for bacteria to undergo transformation is its ability to take up free, extracellular genetic material. Such bacteria are termed as competent cells.
The factors that regulate natural competence vary between various genera. Once the transforming factor (DNA) enters the cytoplasm, it may be degraded by nucleases if it is different from the bacterial DNA. If the exogenous genetic material is similar to bacterial DNA, it may integrate into the chromosome. Sometimes the exogenous genetic material may co-exist as a plasmid with chromosomal DNA.
The phenomenon of natural transformation has enabled bacterial populations to overcome great fluctuations in population dynamics and overcome the challenge of maintaining the population numbers during harsh and extreme environmental changes. During such conditions some bacterial genera spontaneously release DNA from the cells into the environment free to be taken up by the competent cells. The competent cells also respond to the changes in the environment and control the level of gene acquisition through natural transformation process.
Figure 1: Schematic representation of transformation in bacteria
Not all bacteria are capable of taking up exogenous DNA from their environment. The practical approach to acquire competent cells is to make the bacterial cells artificially competent using chemicals or electrical pulses.
Note: To endure the heat shock treatment, it is important the cells used are in the log phase of growth
Sigma-Aldrich offers a wide range of chemically competent cells and electrocompetent cells. Choose the right product for you with our Selection Guide.
The phenomenon of transformation has been widely used in molecular biology. As they are easily grown in large numbers, transformed bacteria may be used as host cells for the following:
The materials required and the detailed protocol of transformation can be found here.
The transformation efficiency is defined as the number of transformants generated per µg of supercoiled plasmid DNA used in the transformation reaction.
Transformation efficiency is calculated using the formula below:
Number of Colonies on Plate (df) | X 1000 ng/µg |
Amount of DNA plated (ng) |
Transformation | Transfection |
Applicable to bacteria | Applicable to eukaryotic cells* |
Exogenous genetic material is taken up by competent bacteria | Exogenous genetic material is introduced into the eukaryotic cells |
Bacteria can be made competent either chemically or by electroporation | Introduction of exogenous genetic material may be liposome-mediated, by electroporation or by using viral vector |
The exogenous genetic material may integrate into the bacterial genome or exist as a plasmid | The exogenous genetic material is either integrated into the genome or is degraded |
Transformation enables the expression of multiple copies of DNA resulting in large amounts of protein or enzyme that are not normally expressed by bacteria |
Genetic material of transformed bacteria may be used to transfect eukaryotic cells for DNA or protein expression studies |
* Eukaryotic cells that undergo cellular changes and become malignant by increased proliferation are also referred to as "transformed" cells. This transformation is due to dysregulation at gene, mRNA and/or protein level and does not resemble transformation in bacteria.
Application | Product No. | Product Description | Transformation Efficiency | Genotype | Blue White Screening Capable |
---|---|---|---|---|---|
for protein expression and DNA plasmid production | CMC0001 | SIG10 Chemically Competent Cells | ≥ 1 × 108 | F- mcrA Δ(mrr-hsdRMS-mcrBC) endA1 recA1 Φ80dlacZΔM15 ΔlacX74 araD139 Δ(ara,leu)7697 galU galK rpsL nupG λ- tonA | Y |
for protein expression and DNA plasmid production | CMC0002 | SIG10 F' Chemically Competent Cells | ≥ 5 × 108 | [F´ pro A+B+ lacIqZΔM15::Tn10 (TetR)] /mcrA Δ(mrr-hsdRMS-mcrBC) endA1 recA1 Φ80dlacZΔM15 ΔlacX74 araD139 Δ(ara, leu)7697 galU galK rpsL nupGλ tonA | Y |
for protein expression and DNA plasmid production | CMC0003 | SIG10 HIGH Electrocompetent Cells | ≥ 5 × 109 | F- mcrA Δ(mrr-hsdRMS-mcrBC) endA1 recA1 Φ80dlacZΔM15 ΔlacX74 araD139 Δ(ara,leu)7697galU galK rpsL nupG λ- tonA (StrR) | Y |
for protein expression and DNA plasmid production | CMC0004 | SIG10 MAX Electrocompetent Cells | ≥ 2 × 1010 | F- mcrA Δ(mrr-hsdRMS-mcrBC) endA1 recA1 Φ80dlacZΔM15 ΔlacX74 araD139 Δ(ara,leu)7697galU galK rpsL nupG λ- tonA (StrR) | Y |
for general cloning & library production | CMC0005 | SIG10 F' MAX Electrocompetent Cells | ≥ 2 × 1010 | [F´ pro A+B+ lacIqZΔM15::Tn10 (TetR)] /mcrA Δ(mrr-hsdRMS-mcrBC) endA1 recA1 Φ80dlacZΔM15 ΔlacX74 araD139 Δ(ara, leu)7697 galU galK rpsL nupG λ- tonA (StrR) | Y |
for general cloning & library production | CMC0006 | SIG10 ULTRA Electrocompetent Cells |
≥ 4 × 1010 | F- mcrA Δ(mrr-hsdRMS-mcrBC) endA1 recA1 Φ80dlacZΔM15 ΔlacX74 araD139 Δ(ara,leu)7697galU galK rpsL nupG λ- tonA (StrR) | Y |
for general cloning & library production | CMC0007 | SIG10 5a Chemically Competent Cells | ≥ 1 × 108 | fhuA2Δ(argF-lacZ)U169 phoA glnV44 Φ80 Δ(lacZ)M15 gyrA96 recA1 relA1 endA1 thi-1 hsdR17 | Y |
for plasmid production using unstable DNA | CMC0008 | STEADY Chemically Competent Cells | > 1 × 107 | recA13 supE44 ara-14 galK2 lacY1 proA2 rpsL20(StrR) xyl-5 λ– leu mtl-1 F– mcrB mrr hsdS20(rB–, mB–) | N |
for plasmid production using unstable DNA | CMC0009 | STEADY Electrocompetent Cells | > 1 × 107 | recA13 supE44 ara-14 galK2 lacY1 proA2 rpsL20(StrR) xyl-5 λ– leu mtl-1 F– mcrB mrr hsdS20(rB–, mB–) | N |
for making Uracil-containing DNA for mutagenesis | CMC0010 | CHANGER Electrocompetent Cells | 1 × 109 | [F’ Tra+ Pil+ (CamR)] ung-1 relA1 dut-1 thi-1 spoT1 mcrA | N |
for BAC & cosmid cloning | CMC0011 | XLDNA V2 Electrocompetent cells |
≥ 1 × 1010 | F- mcrA Δ(mrr-hsdRMS-mcrBC) endA1 recA1 Φ80dlacZΔM15 ΔlacX74 araD139 Δ(ara,leu)7697 galUgalK rpsL nupG (attL araC-PBAD-trfA250 bla attR) λ- | Y |
for BAC & cosmid cloning | CMC0012 | XLDNA SIG10 Electrocompetent cells | ≥ 1 × 1010 | F - pro A+B+ lacIqZΔM15::Tn10 (TetR)] /mcrA Δ(mrr-hsdRMS-mcrBC) endA1 recA1 Φ80dlacZΔM15 ΔlacX74 araD139 Δ(ara, leu)7697 galU galK rpsL nupG λ- tonA (StrR) | N |
for production of biotinylated proteins | CMC0013 | BIOTINYLATER F' Electrocompetent Cells | >1 ×1010 | MC1061 [F´ pro A+B+ lacIqZΔM15::Tn10 (TetR)] araD139 ∆(ara-leu)7696 ∆(lac)l74 galU galK hsdR2(rΚ- mΚ+) mcrB1 rpsL (StrR) birA | N |
for protein expression | CMC0014 | BL21(DE3) Chemically Competent Cells | ≥ 1 × 107 | F – ompT hsdSB (rB- mB-) gal dcm (DE3) | N |
for protein expression | CMC0015 | BL21(DE3) pLysE Chemically Competent Cells | ≥ 1 × 107 | F – ompT hsdSB (rB- mB-) gal dcm (DE3) | N |
for protein expression | CMC0016 | BL21(DE3) Electrocompetent Cells |
≥ 5 x 109 | F – ompT hsdSB (rB- mB-) gal dcm (DE3) | N |
for the highest protein expression | CMC0017 | OverExpress C41(DE3) Chemically Competent Cells | ≥ 1 × 106 | F – ompT hsdSB (rB- mB-) gal dcm (DE3) | N |
for the highest protein expression | CMC0018 | OverExpress C41(DE3) pLysS Chemically Competent Cells | ≥ 1 × 106 | F – ompT hsdSB (rB- mB-) gal dcm (DE3) pLysS (CmR) | N |
for the highest protein expression | CMC0019 | OverExpress C43(DE3) Chemically Competent Cells | ≥ 1 × 106 | F – ompT hsdSB (rB- mB-) gal dcm (DE3) | N |
for the highest protein expression | CMC0020 | OverExpress C43(DE3) pLysS Chemically Competent Cells | ≥ 1 × 106 | F – ompT hsdSB (rB- mB-) gal dcm (DE3) pLysS (CmR) | N |
for the highest protein expression | CMC0021 | OverExpress C41(DE3) Electrocompetent Cells |
≥ 1 × 109 | F – ompT hsdSB (rB- mB-) gal dcm (DE3) | N |
for the highest protein expression | CMC0022 | OverExpress C43(DE3) Electrocompetent Cells | ≥ 1 × 109 | F – ompT hsdSB (rB- mB-) gal dcm (DE3) | N |
for controlled protein expression | CMC0023 | CONTROLLER SIG10 Chemically Competent Cells | > 1 × 109 | mcrA Δ(mrr-hsdRMS-mcrBC) endA1 recA1 ɸ80dlacZΔM15 ΔlacX74 araD139 Δ (ara,leu)7697 galU galK rpsL (StrR) nupG λ− tonA Mini-F lacIq1 (GentR) | N |
for controlled protein expression | CMC0024 | CONTROLLER BL21(DE3) Chemically Competent Cells | > 1 × 107 | F- ompT hsdSB (rB- mB-) gal dcm (DE3) Mini-F lacIq1(GentR) | N |
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