This efficiency can be affected by a number of factors, including the method used for introducing the DNA, the type of cell and plasmid used, and the conditions under which the transformation is performed.
Therefore, measuring and optimizing transformation efficiency is an important step in many molecular biology applications, including genetic engineering, gene therapy and biotechnology.
This can be calculated by multiplying the number of colonies by the volume of the culture plated and dividing by the amount of DNA used.
Individual cells are capable of taking up many DNA molecules, but the presence of multiple plasmids does not significantly affect the occurrence of successful transformation events.
The presence of contaminants as well as ligase in a ligation mixture can reduce the transformation efficiency in electroporation,[17] and inactivation of ligase or chloroform extraction of DNA may be necessary for electroporation, alternatively only use a tenth of the ligation mixture to reduce the amount of contaminants.
Protocols for chemical method however exist for making super competent cells that may yield a transformation efficiency of over 1 x 109.
[19] Adding cytidine or guanosine to the electrophoresis buffer at 1 mM concentration however may protect the DNA from damage.
[20] Electroporation tends to be more efficient than chemical methods and can be applied to a wide range of species and to strains that were previously resistant and recalcitrant to transformation techniques.
However, a transformation efficiencies as high as 0.5-5 x 1010 colony forming units (CFU) per microgram of DNA for E. coli.
For samples that are hard to handle, like cDNA libraries, gDNA, and plasmids larger than 30 kb, it is suggested to use electrocompetent cells that have transformation efficiencies of over 1 x 1010 CFU/μg.
This will ensure a high success rate in introducing the DNA and forming a large number of colonies.
[23] It is important to adjust and optimize the electroporation buffer (Increasing the concentration of the electroporation buffer can result in increased transformation efficiencies ) and the shape, strength, number, and number of pulses these electrical parameters play a key role in transformation efficiency.
However, these methods resulted in transformation efficiencies, with a maximum of 105 - 106 colony forming units (CFU) per microgram of plasmid DNA.
To address this problem, strategies such as altering the methylation of the exogenous DNA using commercial methylases or reducing the restriction activity in the recipient cells have been applied.