Isolation and characterization of a plasmid from phase I Coxiella burnetii

Abstract

The DNA from the Nine Mile phase I strain of C. burnetii, the etiological agent of Q fever, was isolated and purified by CsCl-ethidium bromide density gradient centrifugation. A fraction of this DNA had a density characteristic of plasmid DNA. The plasmid DNA was cut with 20 different restriction endonucleases and shown to be a discrete entity. The plasmid, designated QpH1, is .apprx. 36 kilobases in size and has a molecular mass of 2.4 .times. 107 daltons. A partial restriction map of QpH1 was constructed by using the restriction endonucleases SalI, KpnI, PstI, and XbaI. QpH1 DNA radioactively labeled by nick translation was used to show that sequences similar to the plasmid are also present in the phase II antigenic variant of C. burnetii.