Characterization of a circular plasmid from Borrelia burgdorferi, etiologic agent of Lyme disease

Borrelia burgdorferi, the etiologic agent of Lyme disease, was recently shown to contain plasmid DNA. Two plasmid species have been described in strain CT1, a Wisconsin tick isolate: a 9.2-kilobase entity; and a larger, 70-kilobase entity. Characterization of the 9.2-kilobase entity by using DNase I and restriction endonucleases demonstrated that the plasmid is supercoiled and exists as a stable dimer in this strain. The role played by the plasmid in B. burgdorferi is unknown.