The clostridial mobilisable transposons (original) (raw)

Abstract.

Mobilisable transposons are transposable genetic elements that also encode mobilisation functions but are not in themselves conjugative. They rely on coresident conjugative elements to facilitate their transfer to recipient cells. Clostridial mobilisable transposons include Tn_4451_ and Tn4452 from Clostridium perfringens, and Tn_4453a_ and Tn_4453b_ from Clostridium difficile, all of which are closely related, and Tn_5398_ from C. difficile. The Tn_4451_ group of elements encodes resistance to chloramphenicol and is unusual in that transposition is dependent upon a large resolvase protein rather than a more conventional transposase or integrase. This group of elements also encodes the mobilisation protein TnpZ that, by acting at the RSA or oriT site located on the transposon, and in the presence of a coresident conjugative element, promotes the movement of the nonreplicating circular intermediate and of plasmids on which the transposon resides. The erythromycin resistance element Tn_5398_ is unique in that it encodes no readily identifiable transposition or mobilisation proteins. However, the element is still capable of intraspecific transfer between C. difficile isolates, by an unknown mechanism. The detailed analysis of these mobilisable clostridial elements provides evidence that the evolution and dissemination of antibiotic resistance genes is a complex process that may involve the interaction of genetic elements with very different properties.

Keywords: Key words. Clostridia; transposon; mobilisation; antibiotic resistance; resolvase.

Footnotes

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