The R1 Plasmid is a

plasmid A plasmid is a small, extrachromosomal DNA molecule within a cell that is physically separated from chromosomal DNA and can replicate independently. They are most commonly found as small circular, double-stranded DNA molecules in bacteria; howev ...

that was first isolated from ''

Salmonella paratyphi ''Salmonella enterica'' subsp. ''enterica'' is a subspecies of ''Salmonella enterica'', the rod-shaped, flagellated, aerobic, Gram-negative bacterium. Many of the pathogenic serovars of the ''S. enterica'' species are in this subspecies, includin ...

bacteria Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were am ...

in 1963. It is a short plasmid, composed of 97,566 nucleotides and 120 genes, that belongs to the IncFII plasmid group.

The R1 plasmid imparts multi-drug

antibiotic resistance Antimicrobial resistance (AMR) occurs when microbes evolve mechanisms that protect them from the effects of antimicrobials. All classes of microbes can evolve resistance. Fungi evolve antifungal resistance. Viruses evolve antiviral resistanc ...

to its host bacteria. It's known as a "low copy" plasmid, meaning that it exists in relatively few copies in any given bacteria. This characteristic allows the R1 plasmid to have an efficient plasmid stabilization system, that aids in stabilizing medium copy number plasmids. R1 must rely on "Type II" segregation system. This plasmid system ensures that at least one copy is contained in each daughter cell after cell division.

Partitioning System

The R1 plasmid partitioning is a mechanism needed for the inheritance of the R1 plasmid. The par system is composed of the ParR and the parC regions, that interact together. The par system determines the position of the replicon, ensuring that at the end of DNA Replication, the plasmid copies are well-positioned to start cell division. The par system also allows for the initiation of ParM formation. ParM produces two important cytoskeletal proteins, MreB, and actin. ParM is directed to move the plasmid copies to opposite cell poles. Cell division takes place, resulting in the partitioned plasmids in two daughter cells. Some genes on the R1 plasmid are: *

ParM Parm or PARM may refer to: * Parmesan cheese, especially in dishes such as chicken parm * PARM 1 mine, Panzer-Abwehr Richtmine (German, ''Antitank defense arranging mine'') * '' Authentic Party of the Mexican Revolution'', Partido Auténtico de la ...

is a prokaryotic actin homologue which provides the force to drive copies of the R1 plasmid to opposite ends of rod shaped bacteria before division. *The

Hok/sok system The hok/sok system is a postsegregational killing mechanism employed by the R1 plasmid in ''Escherichia coli''. It was the first type I toxin-antitoxin pair to be identified through characterisation of a plasmid-stabilising locus. It is a type I s ...

a post-segregational killing system of the plasmid. * CopA-like RNA, an antisense RNA involved in replication control of the plasmid.

References

{{cell-biology-stub Plasmids