transformation processes in biotechnology

Dear student, 

Transformation is the process of introduction of derived DNA fragments from a donor bacteria into a recipient bacteria. It also involves the transfer of naked DNA from donor cell to recipient cell.
It was first demonstrated by Griffith's experiment:

Transforming Principle

• Griffith performed experiments with  the bacteria  Streptococcus pneumoniae . This bacterium has two strains − S strain and R strain.

S strain Bacteria	R strain Bacteria
Produce smooth colonies on culture plate	Produce rough colonies on culture plate
Have a polysaccharide coat	Do not have a polysaccharid e coat
Virulent (causes  pneumonia)	Non-virulent (does not cause pneumonia)

• Griffith’s experiment

• Live R st rain in the presence of heat-killed S strain produce virulence because somehow R strain bacteria is transformed by heat-killed S strain bacteria. Hence, it was concluded that there must be transfer of genetic material.
  This is termed as transformation.
  
   

Now a days, artificial transformation is done by following method:

Before transformation, bacteria are treated with a chemical called calcium chloride, which causes water to enter into the cells and makes them swell. These swollen bacteria are then known as competent bacteria.

Next, plasmid DNA (containing the foreign DNA) is mixed with the competent bacteria and the solution is heated. The plasmid DNA enter the bacteria through small pores created in the cell membranes. Once in the host cell, the plasmid DNA is copied many times by the bacteria’s own DNA replicating machinery.

After transformation, bacteria are grown on a nutrient rich media to test the presence of plasmid DNA. Only transformed bacteria containing a plasmid with antibiotic resistance will grow in the presence of antibiotic.

Hope its helpful.

Regards