- A self-replicating (autonomous) circle of DNA distinct from the chromosomal genome of bacteria. A plasmid contains genes normally not essential for cell growth or survival. Some plasmids can integrate into the host genome, be artificially constructed in the laboratory, and serve as vectors (carriers) in cloning.
* * *A genetic particle physically separate from the chromosome of the host cell (chiefly bacterial) that can stably function and replicate and usually confer some advantage to the host cell; not essential to the cell's basic functioning. SYN: extrachromosomal element, extrachromosomal genetic element, paragene. [cytoplasm + -id]- bacteriocinogenic plasmids bacterial plasmids responsible for the elaboration of bacteriocins. SYN: bacteriocin factors, bacteriocinogens.- conjugative p. a p. that can effect its own intercellular transfer by means of conjugation; this transfer is accomplished by a bacterium being rendered a donor, usually with specialized pili. SYN: infectious p., transmissible p..- F p. the prototype conjugative p. associated with conjugation in the K-12 strain of Escherichia coli. SYN: fertility factor, sex factor.- infectious p. SYN: conjugative p..- nonconjugative p. a p. that cannot effect conjugation and self-transfer to another bacterium (bacterial strain); transfer depends upon mediation of another (and conjugative) p..- R plasmids SYN: resistance plasmids.- resistance plasmids plasmids carrying genes responsible for antibiotic (or antibacterial drug) resistance among bacteria (notably Enterobacteriaceae); they may be conjugative or nonconjugative plasmids, the former possessing transfer genes (resistance transfer factor) lacking in the latter. SYN: R factors, R plasmids, resistance factors, resistance-transferring episomes.- transmissible p. SYN: conjugative p..
* * *plas·mid 'plaz-məd n an extrachromosomal ring of DNA that replicates autonomously and is found esp. in bacteria compare EPISOME
* * *plas·mid (plazґmid) [plasm + -id] an extrachromosomal self-replicating structure found in bacterial cells that carries genes for a variety of functions not essential for cell growth. Plasmids consist of cyclic double-stranded DNA molecules, replicating independently of the chromosomes and transmitting through successive cell divisions genes specifying such functions as antibiotic resistance (R plasmid); conjugation (F plasmid); the production of enzymes, toxins, and antigens; and the metabolism of sugars and other organic compounds. Plasmids can be transferred from one cell to another by conjugation and by transduction. Some plasmids may also become integrated into the bacterial chromosome; these are known as episomes.
Medical dictionary. 2011.