(redirected from Plasmids)
Also found in: Dictionary, Thesaurus, Medical.
Related to Plasmids: Restriction enzymes


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 ?
We hypothesised that since Acriflavine has a negative influence on plasmids, maybe it could have similar negative effects on conjugational transfer too.
733 kb) is closely related to 9 other sequenced mcr-1 plasmids (differing by only a few single nucleotide changes in backbone regions), some of which carry ISApl1 upstream of mcr-1, another IS, or both (Table).
A plasmid is a circular piece of DNA that contains functional DNA fragments that control gene expression in cells.
Within the species of Enterococcus, nighty five plasmids were identified and most of these plasmids were found in Enterococcus faecalis (twenty seven plasmids) and Enterococcus faecium (fifty three plasmids), these two species have become an increasing medical concern by their ability to gain and spread antibiotic resistance.
The plasmid is designed to reduce the cost of AAV manufacturing and subsequent gene therapy applications, while helping Aldevron's clients meet regulatory requirements.
KPC-2] region as that found on pKPHS2 and the plasmids of this type were all found among the ST11 isolates.
Further studied are needed to assess the efficacy of vaccination in chicken with these delivery systems delivering recombinant expression plasmids encoding vp2 against IBDV.
flexneri the analysis of plasmid DNA revealed that all the isolates contained a heterogeneous population of plasmids ranging between greater than 23.
Althea Technologies and Profectus BioSciences have signed a manufacturing supply agreement for plasmid DNA production.
Prediction of the restriction profile with the expected sizes of the DNA fragments that plasmid gWiz HBs and control plasmids would generate after compelte digestion by the various endonclases was performed using New england Biolabs software's NEB cutterV2.