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Transformation

Transformation is the uptake and integration of extracellular DNA into the cells. Cell-to-cell contact is not required in transformation. For the transformation to be successful, several aspects must be fulfilled:

  • The cell should be competent

  • The DNA should exist outside the cell. The DNA can be circular (plasmid) or linear.

  • After intake, the foreign DNA should be incorporated into the chromosome or stabilized in the form of a plasmid.

Only a handful of bacteria species (e.g. Neisseria gonorrhoeae) able to perform a transformation under normal bacteria growth condition (natural competent). Bacteria's competence can be induced by the presence of peptides, nutritional status, or other stressful conditions such as the presence of antibiotics.

Poster presenting 6 stages of transformation. At the first stage, named binding, a linear DNA strand is attached to the cell wall of the bacteria. During the second stage, named fragmentation, DNA strands are fragmented. During the third stage, transport, DNA is linearised and transported through a bacterial cell wall. In the fourth stage, uptake, linear DNA fragments are present inside the bacteria cytoplasm. In the fifth stage, lysis, those fragments can be lysed, thus destroyed by the cell. In the last stage, called integration, DNA fragments that were not destroyed during lysis can be incorporated into the bacterial chromosome.

Figure 1. Steps in transformation. Right: Gram-Negative bacteria, Left: Gram-Positive bacteria. 1) Binding: The naked DNA strands bind to the cells. 2) Fragmentation: Cell's enzymes cut the DNA to smaller pieces. 3) Transport: Cell's protein assists the intake of DNA into the cells (nucleus for Eukaryotes). 4) Uptake: DNA successfully enters the cell. DNA can be destroyed (5-Lysis) or incorporated into the genome (6- Integration).

Transformation is also an important biotechnology technique. It has been used to insert a gene of interest to a bacteria cell; thus creating a recombinant cell.

Referred from:

Article
Horizontal gene transfer