Bacterial Plasmids

Abstract

Plasmids are nonessential genetic elements that can maintain accessory genetic information and facilitate infectious spread of the genes they carry. They regulate their own replication and transmission and were largely responsible for the proliferation of antibiotic resistance during the second half of the twentieth century.

Keywords: extrachromosomal DNA; gene cloning; antibiotic resistance; gene transfer; DNA replication

Figure 1.

Alternative plasmid structures: (a) supercoiled circular plasmid; (b) linear ‘racket frame’ structure and (c) an ‘endless linear’ plasmid (5′‐ and 3′‐DNA termini are joined by a single‐strand loop).

Figure 2.

Segregation of incompatible plasmids.

Figure 3.

Control of replication by antisense RNA in plasmid ColE1. ColE1 illustrates the way that antisense RNA can provide a simple negative feedback loop that controls replication in step with cell growth. RNA I is produced in large quantities but is unstable so its concentration is proportional to plasmid copy number. RNA II is made at low level but is more stable and folds in a way that allows association with the replication origin before RNAaseH processing. RNA II transiently forms a structure that associates with hairpin loops of RNA I and is inactivated, so when copy number is high and RNA I concentration is high, very little RNA I is allowed to proceed to form primer for replication. Rom promotes the association of RNA I and II and so further reduces copy number.

Figure 4.

Replication control of the P1 prophage by plasmid handcuffing (a) the R‐replicon of phage P1; iterons flanking repA are indicated by arrows (b) following replication, plasmid pairing is mediated by iteron‐bound RepA and eventually disrupted by partition and cell division.

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References

Bergquist PL (1987) Incompatibility. In: Hardy KG (ed.) Plasmids: A Practical Approach, pp. 37–78. Oxford: IRL Press.

Bingle LEH and Thomas CM (2001) Regulatory circuits for plasmid survival. Current Opinion in Microbiology 4: 194–200.

Chant EL and Summers DK (2007) Indole signalling contributes to the stable maintenance of E. coli multicopy plasmids. Molecular Microbiology 63: 35–43.

Chattoraj DK (2000) Control of plasmid DNA replication by iterons: no longer paradoxical. Molecular Microbiology 37: 467–476.

Ebersbach G, Sherratt DJ and Gerdes K (2005) Partition‐associated incompatibility caused by random assortment of pure plasmid clusters. Molecular Microbiology 56: 1430–1440.

Frost LS, Leplae R, Summers AO and Toussaint A (2005) Mobile genetic elements: the agents of open source evolution. Nature Reviews. Microbiology 3: 722–732.

Gerdes K and Wagner EGH (2007) RNA antitoxins. Current Opinion in Microbiology 10: 117–124.

Hayes F and Barillà D (2006) The bacterial segrosome: a dynamic nucleoprotein machine for DNA trafficking and segregation. Nature Reviews. Microbiology 4: 133–143.

Mazel D (2006) Integrons: agents of bacterial evolution. Nature Reviews. Microbiology 4: 608–620.

del Solar G and Espinosa M (2000) Plasmid copy number control: an ever‐growing story. Molecular Microbiology 37: 492–500.

Summers DK (1998) Timing, self control and a sense of direction are the secrets of multicopy plasmid stability. Molecular Microbiology 29: 1137–1145.

Top EM, Moënne‐Loccoz Y, Pembroke T and Thomas CM (2000) Phenotypic traits conferred by plasmids. In: Thomas CM (ed.) The Horizontal Gene Pool: Bacterial Plasmids and Gene Spread, pp. 249–285. Amsterdam: Harwood Academic Press.

Zechner EL, de la Cruz F, Eisenbrandt R et al. (2000) Conjugative‐DNA transfer processes. In: Thomas CM (ed.) The Horizontal Gene Pool: Bacterial Plasmids and Gene Spread, pp. 87–174. Amsterdam: Harwood Academic Press.

Further Reading

Bushman F (2001) Lateral DNA Transfer. New York: Cold Spring Harbor Laboratory Press.

Funnell BE and Phillips GJ (eds) (2004) Plasmid Biology. Washington, DC: ASM Press.

Grinstead J and Bennett PM (1988) Plasmid technology. In: Methods in Microbiology. London: Academic Press.

Hardy KG (1987) Plasmids: A Practical Approach. Oxford: IRL Press.

Hardy KG (1993) Plasmids: A Practical Approach. Oxford: IRL Press.

Snyder L and Champness W (2002) Molecular Genetics of Bacteria. Washington, DC: ASM Press.

Summers DK (1996) The Biology of Plasmids. Oxford: Blackwell Science.

Syvanen M and Kado CI (2002) Horizontal Gene Transfer. Amsterdam: Elsevier.

Thomas CM (ed.) (2000) The Horizontal Gene Pool: Bacterial Plasmids and Gene Spread. Amsterdam: Harwood Academic Press.

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How to Cite close
Thomas, Christopher M, and Summers, David(Sep 2008) Bacterial Plasmids. In: eLS. John Wiley & Sons Ltd, Chichester. http://www.els.net [doi: 10.1002/9780470015902.a0000468.pub2]