English: Natural competence is a unique ability of bacterial cells to take up loose DNA in their natural environments and express it as their own. Most of the time, DNA becomes available naturally because of the death of nearby similar cells. This process begins by allowing the DNA to be transported through either the cell membrane or the cell wall. Once the DNA is inside the cell boundaries, it can either be broken down into nucleotides and used to perform replication or recombined into the cell’s own genome using DNA repair enzymes. If the recombination results in a change in the cell’s genotype, the bacterial cell has been transformed. Most naturally competent bacteria possess type 4 pili which are involved in the transformation process, allowing DNA to enter the cell by way of DNA translocase.

Caption: Key: 1-Bacterial cell DNA 2-Bacterial cell plasmids 3-Sex pili 4-Plasmid of foreign DNA from a dead cell 5-Bacterial cell restriction enzyme 6-Unwound foreign plasmid 7-DNA ligase

I: A plasmid of foreign DNA from a dead cell is intercepted by the sex pili of a naturally competent bacterial cell. II: The foreign plasmid is transduced through the sex pili into the bacterial cell, where it is processed by bacterial cell restriction enzymes. The restriction enzymes break the foreign plasmid into a strand of nucleotides that can be added to the bacterial DNA. III: DNA ligase integrates the foreign nucleotides into the bacterial cell DNA. IV: Recombination is complete and the foreign DNA has integrated into the original bacterial cell’s DNA and will continue to be a part of it when the bacterial cell replicates next.

Image Sources: http://www.biotechlearn.org.nz/themes/dna_lab/bacterial_transformation http://202.204.115.67/jpkch/jpkch/2008/wswx/chapter%2010/16.jpg

http://en.wikipedia.org/wiki/Natural_competence