Bacterial Transformation – Horizontal Gene Transfer Part – II
Bacterial transformation is a horizontal gene transfer method in bacteria and it was discovered by Fred Griffith in 1928.
Bacterial transformation is the uptake of a naked DNA molecule or a fragment of DNA by a cell and its incorporation into the recipient chromosome.
Mechanism:
Natural transformation: In natural condition, when a bacteria lyse, it release its DNA into the surrounding environment. When these fragments containing several genes comes in contact with a COMPETENT cell, it binds to the cell and it will be taken up by the competent cell.
Competent cell: a cell that is in certain stage of growth where it can take up a DNA from outside. For example, Streptococcus Pneumoniae becomes competent during exponential phase. It secrets a small protein called competence factor which stimulates the production of 8-10 new proteins which are required for the DNA transformation.
In nature, DNA transformation occurs in soil and marine environment.
Artificial transformation: is carried out in the lab by various techniques such as treating the bacterial cells with calcium chloride which makes the cells competent and thus it can take up the DNA. In artificial transformation, a circular plasmid is used in order to prevent its degradation and easy replication once within the host.
Understand the other two methods of horizontal gene transfer in bacteria here – Conjugation and Transduction.