How are competent cells prepared in transformation?
Competent cells are the one those have cell membrane which are more permeable than normal cells so that DNA can be passed through these type of cells easily. Since DNA is a water loving molecule it would not pass through the bacterial cell membrane and to make the cells capable of internalising the genetic material they are made competent so that they would take up the DNA.
Two methods are there for the preparation competent cells. They are calcium chloride method and electroporation.
Calcium chloride method:
This is the most efficient method for the preparation of competent cells. Calcium chloride will increase the ability of the bacterial cell to incorporate plasmid DNA which then facilitates genetic transformation. Calcium chloride treatment will allow the binding of plasmid DNA to LPS present in the outer layer of bacterial cell wall and both the negatively charged DNA and LPS will come in contact and when heat shock is applied plasmid DNA will pass into the bacterial cell.
Cells were first treated with calcium chloride by suspending them in the cold solution that has high concentration of calcium. The purpose of using cold solution is making the bacterial membrane stabilise and to increase the interaction between the calcium cation and negatively charged components. DNA can be then forced into the cells by applying heat shock at 42°C of the process of transformation. The purpose of applying heat shock is it can alter the fluidity of the membrane and when it changes, DNA can pass into the bacterial cell efficiently.
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