Editing Plasmid (section)

==Plasmid maintenance==
{{main|Addiction module}}
Some plasmids or microbial hosts include an [[addiction module|addiction system]] or postsegregational killing system (PSK), such as the [[hok/sok system|hok/sok]] (host killing/suppressor of killing) system of plasmid R1 in ''[[Escherichia coli]]''.<ref>{{cite journal | vauthors = Gerdes K, Rasmussen PB, Molin S | title = Unique type of plasmid maintenance function: postsegregational killing of plasmid-free cells | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 83 | issue = 10 | pages = 3116–3120 | date = May 1986 | pmid = 3517851 | pmc = 323463 | doi = 10.1073/pnas.83.10.3116 | doi-access = free | bibcode = 1986PNAS...83.3116G }}</ref> This variant produces both a long-lived [[poison]] and a short-lived [[antidote]]. Several types of plasmid addiction systems (toxin/ antitoxin, metabolism-based, ORT systems) were described in the [[literature]]<ref>{{cite journal | vauthors = Kroll J, Klinter S, Schneider C, Voss I, Steinbüchel A | title = Plasmid addiction systems: perspectives and applications in biotechnology | journal = Microbial Biotechnology | volume = 3 | issue = 6 | pages = 634–657 | date = November 2010 | pmid = 21255361 | pmc = 3815339 | doi = 10.1111/j.1751-7915.2010.00170.x }}</ref> and used in biotechnical (fermentation) or biomedical (vaccine therapy) applications. Daughter cells that retain a copy of the plasmid survive, while a daughter cell that fails to inherit the plasmid dies or suffers a reduced growth-rate because of the lingering poison from the parent cell. Finally, the overall productivity could be enhanced.{{Clarification needed|reason=The productivity of what? Enhanced by what? Is this sentence placed here by mistake?|date=October 2024}}

In contrast, plasmids used in biotechnology, such as pUC18, pBR322 and derived vectors, hardly ever contain toxin-antitoxin addiction systems, and therefore need to be kept under antibiotic pressure to avoid plasmid loss.