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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



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.



An extrachromosomal genetic element found among various strains of Escherichia coli and other bacteria.
References in periodicals archive ?
Plasmid pYHCC carries 4 antimicrobial resistance genes, all of which are in the multidrug resistance region.
This quality testing level is exclusively based on molecular biology techniques such as DNA agarose gel electrophoresis, restriction digestion and analysis [19- 20] of the plasmid restriction profile along with plasmid DNA sequencing [21].
The pMB1 origin of replication produces two RNA molecules, which regulate plasmid replication.
Antiplasmid testing: The plasmid curing was performed by method described by Deshpande et al (24).
Other than the Plasmids and Tonics, the sense of morality that Bioshock 2 places on the player is also what makes it so different.
Students can be provided with a copy of a protocol for plasmid DNA isolation that has explanations for each step.
We are continuing to expand our collaborative development services to meet the growing needs for a wide variety of plasmid based products.
The concept that fimbriae=pili=BNT are the elongated protein appendages, conditionally controlled by Plasmid DNA.
Second, based on its DNA sequence, plasmid pMA67 is thought to have the ability to transfer to other bacterial cells in a process called "plasmid mobilization.
9%--of the plasmid in some labeled strains grown for five consecutive subcultures in the absence of selective pressure.
Plasmids were extracted using a High Pure Plasmid Isolation Kit (Roche, 2003).
Four plasmids appears to be the ideal number: "If we don't worry about just generation of virus, we can make a virus with one plasmid," says Kawaoka.