Editing Plasmid (section)

{{Short description|Small DNA molecule within a cell}}
{{about|the DNA molecule|the physics phenomenon|plasmoid}}
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[[File:plasmid (english).svg|thumb|upright=1.35|Diagram of a bacterium showing chromosomal DNA and plasmids (Not to scale)]]
A '''plasmid''' is a small, [[extrachromosomal DNA]] molecule within a cell that is physically separated from [[gDNA|chromosomal DNA]] and can replicate independently. They are most commonly found as small circular, double-stranded DNA molecules in [[bacteria]]; however, plasmids are sometimes present in [[archaea]] and [[eukaryote|eukaryotic organisms]].<ref>{{cite book |vauthors=Esser K, Kück U, Lang-Hinrichs C, Lemke P, Osiewacz HD, Stahl U, Tudzynski P |title=Plasmids of Eukaryotes: fundamentals and Applications |date=1986 |publisher=Springer-Verlag |location=Berlin |isbn=978-3-540-15798-4}}</ref>{{page needed|date=December 2024}}<ref>{{cite book  |chapter=Mitochondrial and Chloroplast Plasmids |pages=81–146 |veditors=Wickner RB, Hinnebusch A, Lambowitz AM, Gunsalus IC, Hollaender A  |title=Extrachromosomal Elements in Lower Eukaryotes |date=1987 |publisher=Springer US |location=Boston, MA |isbn=978-1-4684-5251-8 }}</ref> Plasmids often carry useful genes, such as those involved in [[antibiotic resistance]], [[virulence]],<ref name="Smillie_2010">{{cite journal |vauthors=Smillie C, Garcillán-Barcia MP, Francia MV, Rocha EP, de la Cruz F |title=Mobility of plasmids |journal=Microbiology and Molecular Biology Reviews |volume=74 |issue=3 |pages=434–452 |date=September 2010 |pmid=20805406 |pmc=2937521 |doi=10.1128/MMBR.00020-10 }}</ref><ref name="Carattoli_2013">{{cite journal |vauthors=Carattoli A |title=Plasmids and the spread of resistance |journal=International Journal of Medical Microbiology |volume=303 |issue=6–7 |pages=298–304 |date=August 2013 |pmid=23499304 |doi=10.1016/j.ijmm.2013.02.001 |series=Special Issue Antibiotic Resistance }}</ref><ref name=":1">{{Cite journal |last1=San Millan |first1=Alvaro |last2=MacLean |first2=R. Craig |date=2017-09-22 |editor-last=Baquero |editor-first=Fernando |editor2-last=Bouza |editor2-first=Emilio |editor3-last=Gutiérrez-Fuentes |editor3-first=J.A. |editor4-last=Coque |editor4-first=Teresa M. |title=Fitness Costs of Plasmids: a Limit to Plasmid Transmission |journal=Microbiology Spectrum |volume=5 |issue=5 |doi=10.1128/microbiolspec.MTBP-0016-2017 |pmid=28944751 |pmc=11687550 }}</ref> [[secondary metabolism]]<ref>{{cite journal |last1=Saati-Santamaría |first1=Zaki |title=Global Map of Specialized Metabolites Encoded in Prokaryotic Plasmids |journal=Microbiology Spectrum |date=17 August 2023 |volume=11 |issue=4 |pages=e0152323 |doi=10.1128/spectrum.01523-23 |pmid=37310275 |pmc=10434180 }}</ref> and [[bioremediation]].<ref>{{cite journal |last1=Bhatt |first1=Pankaj |last2=Bhandari |first2=Geeta |last3=Bhatt |first3=Kalpana |last4=Maithani |first4=Damini |last5=Mishra |first5=Sandhya |last6=Gangola |first6=Saurabh |last7=Bhatt |first7=Rakesh |last8=Huang |first8=Yaohua |last9=Chen |first9=Shaohua |title=Plasmid-mediated catabolism for the removal of xenobiotics from the environment |journal=Journal of Hazardous Materials |date=October 2021 |volume=420 |pages=126618 |doi=10.1016/j.jhazmat.2021.126618 |pmid=34329102 |bibcode=2021JHzM..42026618B }}</ref><ref>{{cite journal |last1=Saati-Santamaría |first1=Zaki |last2=Navarro-Gómez |first2=Pilar |last3=Martínez-Mancebo |first3=Juan A |last4=Juárez-Mugarza |first4=Maitane |last5=Flores |first5=Amando |last6=Canosa |first6=Inés |title=Genetic and species rearrangements in microbial consortia impact biodegradation potential |journal=The ISME Journal |date=25 January 2025 |doi=10.1093/ismejo/wraf014 |pmid=39861970 |pmc=11892951 }}</ref> While chromosomes are large and contain all the essential genetic information for living under normal conditions, plasmids are usually very small and contain additional genes for special circumstances.

[[Artificial plasmids]] are widely used as [[Vector (molecular biology)|vectors]] in [[molecular cloning]], serving to drive the replication of [[recombinant DNA]] sequences within host organisms. In the laboratory, plasmids may be introduced into a cell via [[transformation (genetics)|transformation]]. Synthetic plasmids are available for procurement over the internet by various vendors using submitted sequences typically designed with software, if a design does not work the vendor may make additional edits from the submission.<ref>{{Cite web |url=https://www.genscript.com/synthetic-biology-gene-synthesis-service.html |title=GenBrick Gene Synthesis - Long DNA Sequences &#124; GenScript}}</ref><ref>{{Cite web |url=https://www.idtdna.com/pages/products/genes-and-gene-fragments/custom-gene-synthesis |title=Gene synthesis &#124; IDT |website=Integrated DNA Technologies}}</ref><ref>{{cite web |url=https://www.thermofisher.com/se/en/home/life-science/cloning/gene-synthesis/geneart-gene-synthesis.html |title=Invitrogen GeneArt Gene Synthesis}}</ref>

Plasmids are considered ''[[replicon (genetics)|replicon]]s'', units of DNA capable of replicating autonomously within a suitable host. However, plasmids, like [[virus]]es, are not generally classified as [[life]].<ref>{{cite journal |vauthors=Sinkovics J, Horvath J, Horak A |title=The origin and evolution of viruses (a review) |journal=Acta Microbiologica et Immunologica Hungarica |volume=45 |issue=3–4 |pages=349–390 |year=1998 |pmid=9873943 }}</ref> Plasmids are transmitted from one bacterium to another (even of another species) mostly through [[Bacterial conjugation|conjugation]].<ref name="Smillie_2010" /> This host-to-host transfer of genetic material is one mechanism of [[horizontal gene transfer]], and plasmids are considered part of the [[mobilome]]. Unlike viruses, which encase their genetic material in a protective protein coat called a [[capsid]], plasmids are "naked" DNA and do not encode genes necessary to encase the genetic material for transfer to a new host; however, some classes of plasmids encode the [[pilus#Conjugative pili|conjugative "sex" pilus]] necessary for their own transfer. Plasmids vary in size from 1 to over 400 k[[base pair|bp]],<ref name="ThomasSummers2008">{{cite encyclopedia |vauthors=Thomas CM, Summers D |chapter=Bacterial Plasmids |year=2008|doi=10.1002/9780470015902.a0000468.pub2 |encyclopedia=Encyclopedia of Life Sciences |isbn=978-0-470-01617-6 }}</ref> and the number of identical plasmids in a single [[cell (biology)|cell]] can range from one up to thousands.