Plasmid stability
Plasmid stability is a bacteriological term that, depending on the context, can have one of two meanings. It is used in connection with statements about the stability of a plasmid in an expression system , usually in a genetically modified bacterial cell .
Structural stability
When a structural plasmid stability is mentioned, a judgment is made about the stability of the shape of a plasmid. A low structural stability is characterized by frequent changes of the plasmid contained in the nucleotide sequences , that is, insertions , deletions or point mutations , out. A high structural plasmid stability is important for genetic engineering processes, since frequent mutations reduce the yield of desired products of a gene modification and undesirable by-products are increasingly formed.
Segregative stability
The term segregative plasmid stability , often just referred to as plasmid stability in this context , indicates the rate at which the proportion of bacterial cells with foreign or modified plasmids within a culture increases or decreases under certain conditions. When cultivating genetically modified bacteria, a high degree of segregative stability is essential. Foreign plasmids or plasmid sequences are usually associated with a disadvantage for a prokaryote when it comes to passing on its DNA , so sooner or later transgenic bacteria will be displaced by unmanipulated bacteria.
A common, frequently used countermeasure is targeted selection by adding a resistance via the foreign DNA, for example an antibiotic resistance that unchanged organisms do not have, and subsequent cultivation on a nutrient medium that is provided with an inhibitor that is only limitedly effective against the transgenic bacteria . In addition, desired plasmid information can also be firmly integrated into the chromosomal structure of the expression system, so that subsequent separation from the added DNA is made significantly more difficult. Both of these measures mentioned by way of example for increasing the segregative plasmid stability can be applied simultaneously.
Individual evidence
- ↑ DK Summers: Stability of genetic material in prokaryotes . Biologicals 21 91-93. 1993.
- ↑ KH Friehs: measures to improve the production of recombinant proteins and plasmid DNA . 1999. Habilitation thesis.