Editing Genetic transformation (section)

===Bacterial===
Artificial competence can be induced in laboratory procedures that involve making the cell passively permeable to DNA by exposing it to conditions that do not normally occur in nature.<ref>{{cite periodical |vauthors=Donahue RA, Bloom FR |title=Large-volume transformation with high-throughput efficiency chemically competent cells |periodical=Focus |volume=20 |issue=2 |pages=54–56 |date=July 1998 |url=http://www.invitrogen.com/etc/medialib/en/filelibrary/pdf/focus.Par.78703.File.dat/Focus%20Volume%2020%20Issue%202.pdf |archive-url=https://web.archive.org/web/20130306120401/http://www.invitrogen.com/etc/medialib/en/filelibrary/pdf/focus.Par.78703.File.dat/Focus%20Volume%2020%20Issue%202.pdf |archive-date=2013-03-06 |oclc=12352630 |via=Invitrogen}}{{rs|date=September 2022|reason=corporate publication where the authors work for the corporation;}}</ref> Typically the cells are incubated in a solution containing [[divalent]] [[cation]]s (often [[calcium chloride]]) under cold conditions, before being exposed to a heat pulse (heat shock). Calcium chloride partially disrupts the cell membrane, which allows the recombinant DNA to enter the host cell. Cells that are able to take up the DNA are called competent cells.

It has been found that growth of Gram-negative bacteria in 20 mM Mg reduces the number of protein-to-[[lipopolysaccharide]] bonds by increasing the ratio of ionic to covalent bonds, which increases membrane fluidity, facilitating transformation.<ref name="Srivastava">{{cite book | last = Srivastava | first = Sheela | name-list-style = vanc | title = Genetics of Bacteria | publisher = [[Springer-Verlag]] | year = 2013 | location = India | url = https://link.springer.com/content/pdf/10.1007%2F978-81-322-1090-0.pdf#page=112| doi = 10.1007/978-81-322-1090-0 | isbn = 978-81-322-1089-4 | s2cid = 35917467 }}</ref> The role of lipopolysaccharides here are verified from the observation that shorter O-side chains are more effectively transformed – perhaps because of improved DNA accessibility.

The surface of bacteria such as ''E. coli'' is negatively charged due to [[phospholipids]] and [[lipopolysaccharide]]s on its cell surface, and the DNA is also negatively charged. One function of the divalent cation therefore would be to shield the charges by coordinating the phosphate groups and other negative charges, thereby allowing a DNA molecule to adhere to the cell surface.

DNA entry into ''E. coli'' cells is through channels known as zones of adhesion or Bayer's junction, with a typical cell carrying as many as 400 such zones. Their role was established when [[cobalamine]] (which also uses these channels) was found to competitively inhibit DNA uptake. Another type of channel implicated in DNA uptake consists of poly (HB):poly P:Ca. In this poly (HB) is envisioned to wrap around DNA (itself a polyphosphate), and is carried in a shield formed by Ca ions.<ref name="Srivastava" />

It is suggested that exposing the cells to divalent cations in cold condition may also change or weaken the cell surface structure, making it more permeable to DNA.  The heat-pulse is thought to create a thermal imbalance across the cell membrane, which forces the DNA to enter the cells through either cell pores or the damaged cell wall.

[[Electroporation]] is another method of promoting competence.  In this method the cells are briefly shocked with an [[electric field]] of 10-20 [[Volt|kV]]/cm, which is thought to create holes in the cell membrane through which the plasmid DNA may enter.  After the electric shock, the holes are rapidly closed by the cell's membrane-repair mechanisms.