| Bacterial transformation is routine work in all | | | | Sudden exposure of this cell to the room |
| molecular biology laboratories as part of | | | | temperature or higher can force the cell to take |
| recombinant DNA experiment or gene cloning. In | | | | the DNA from outside. Take the stored |
| rDNA experiments or gene cloning, we prepare | | | | competent cells, which are in the frozen condition |
| recombinant DNA or the gene or plasmid to be | | | | and add the DNA sample to these cells and |
| cloned, which has to be transferred to a host cell | | | | expose them to a higher temperature, at 42°C |
| so that the DNA will multiply inside the bacterial | | | | for two to three minutes. Some of these cells |
| cell. Transfer of the plasmid or the rDNA is carried | | | | take the DNA from outside and will be |
| out by bacterial transformation. | | | | transformed by intercalating with its genome. |
| The first step is to select a suitable host cell such | | | | These cultures can be plated on a selection agar |
| as a suitable strain of e.coli like DH5 a , a common | | | | plate and the transformed colonies can be |
| strain available in all molecular biology laboratories, | | | | selected against the untransformed ones. |
| which can take foreign DNA easily. For this we | | | | This transformation is extensively used in genetic |
| have to treat the grown bacterial cultures at its | | | | engineering experiments. Any gene or DNA, |
| log phase of growth, with CaCl2. Centrifuge the | | | | before transferring into an organism, can be |
| cells growing at the log phase under low rpm | | | | tested in a selected host by this transformation |
| (3,000-5,000 for 10 minutes) at 4°C and collect | | | | method. New promoters can be checked for their |
| the cells. Suspend the cells in chilled CaCl2 of 0.1 M. | | | | strength of expression. Commercially-useful |
| The cells in calcium chloride are able to accept the | | | | enzymes and therapeutic proteins can be |
| small DNA molecules. These cells in CaCl2 can be | | | | prepared in industrial scales. In short, any genetic |
| stored for a long time under low temperatures | | | | engineering or gene cloning cannot be |
| such as -20 or -70°C. | | | | accomplished without bacterial transformation. |