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Related to Plasmid: Plasmid DNA


A circular extrachromosomal genetic element that is ubiquitous in prokaryotes and has also been identified in a number of eukaryotes. In general, bacterial plasmids can be classified into two groups on the basis of the number of genes and functions they carry. The larger plasmids are deoxyribonucleic acid (DNA) molecules of around 100 kilobase (kb) pairs, which is sufficient to code for approximately 100 genes. There is usually a small number of copies of these plasmids per host chromosome, so that their replication must be precisely coordinated with the cell division cycle. The plasmids in the second group are smaller in size, about 6–10 kb. These plasmids may harbor 6–10 genes and are usually present in multiple copies (10–20 per chromosome). See Gene

Plasmids have been identified in a large number of bacterial genera. Some bacterial species harbor plasmids with no known functions (cryptic plasmids) which have been identified as small circular molecules present in the bacterial DNA. The host range of a particular plasmid is usually limited to closely related genera. Some plasmids, however, are much more promiscuous and have a much broader host range.

The functions specified by different bacterial plasmids are usually quite specialized in nature. Moreover, they are not essential for cell growth since the host bacteria are viable without a plasmid when the cells are cultured under conditions that do not select for plasmid-specified gene products. Plasmids thus introduce specialized functions to host cells which provide versatility and adaptability for growth and survival. Plasmids which confer antibiotic resistance (R plasmids) have been extensively characterized because of their medical importance. Plasmids have played a seminal role in the spectacular advances in the area of genetic engineering. Individual genes can be inserted into specific sites on plasmids in cell cultures and the recombinant plasmid thus formed introduced into a living cell by the process of bacterial transformation. See Genetic engineering

McGraw-Hill Concise Encyclopedia of Bioscience. © 2002 by The McGraw-Hill Companies, Inc.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.



a generic term for any intracellular hereditary factor that is not located within the chromosomes. Plasmids include genetic factors in cell organelles, for example, mitochondria and plastids, as well as genetic factors that are not found in any essential components of cells. Of the plasmids that are not associated with any permanent structure, the most extensively studied are the kappa-particle in paramecia (which produces the antibiotic paramecin), the sensitivity factor for CO2, and the agent that inhibits the occurrence of male Drosophila. In addition, several bacteria possess plasmids. Bacterial plasmids control resistance to medicines and regulate the synthesis of bacteriocin, enterotoxin, hemolysin, and certain antigens. The plasmids that are called sex factors control sexual differentiation in bacteria. It has been shown that many plasmids consist of ring molecules of double-stranded deoxyribonucleic acid with a molecular weight that ranges from 106 to 108 daltons.


The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.


An extrachromosomal genetic element found among various strains of Escherichia coli and other bacteria.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
References in periodicals archive ?
Linear DNA is a form of DNA distinct from the circular form of DNA most commonly produced in plasmids and grown in bacteria.
Having transfection grade plasmid DNA available is critical to today's high value biopharmaceutical applications and working with Macherey-Nagel's proven anion-exchange technology will allow to develop a cost effective automation solution for this important process, added Piero Zucchelli, CEO and co-founder of Andrew Alliance.
anthracis Plasmid gene (CapB) was reported to be 37.9% (11/29) in different villages of Lahore District (Shabbir et al., 2015), which is higher than other districts in current study.
Addgene's frozen plasmid stocks are kept in plastic 2D barcoded vials from Micronic.
coli, the pUC57 plasmid containing the gene coding of huscFv was digested with restriction digestion enzymes Mlsl (Mscl) and Xhol and the insert was subcloned into the Mlsl (Mscl) and Xhol site of pET22b (+) expression vector.
AAV manufacturing has traditionally required unique custom batches of helper plasmids. This can be expensive and time consuming.
Plasmid extraction was done using a commercial plasmid kit (Plasmid Miniprep Kit, Promega Co.USA) and depending on the manufacture instructions: 600[micro]l of lauria broth was prepared and used for growing each one of bacterial isolate, then added to a 1.5 ml microcentrifuge tube.
The map of the plasmid with GC content and GC skew was drawn with the online CGView Server ( cgview_server/) and local GView 1.7 with visual interface [40].
Although the reason why plasmid is lost in the reproductive process is not completely understood by theoretical biologists even at present time, it has been experimentally validated that the plasmid-bearing cells have at least for some substrate concentrations a lower maximum specific growth rate than the plasmid-free counterpart [9,16,17].
Summary: TEHRAN (FNA)- Scientists have design better molecules that make it harder for plasmids to move between bacteria.