Comparison of Coxiella burnetii plasmids to homologous chromosomal sequences present in a plasmidless endocarditis-causing isolate.
Coxiella burnetii is the etiological agent of human Q fever and chronic endocarditis. Different plasmids have been found in C. burnetii isolates and a correlation between disease state and plasmid type has been established. The plasmid QpRS was found in all but four of the endocarditis-causing isolates examined. These four isolates did not contain a detectable plasmid. However, when DNA from the plasmidless isolates is hybridized with 32P-labeled QpRS, homologous sequences are detected. It was hypothesized that plasmid sequences had inserted into the chromosomal DNA of the plasmidless isolate. A cosmid chromosomal gene bank was constructed from one of the plasmidless isolates and a number of clones were obtained. One clone, pEAS137, contained all of the EcoR I fragments with homology to the C. burnetii plasmids plus several non-homologous fragments. The EcoR I fragments in pEAS137 were in the same linear order as present in the chromosome of the plasmidless isolate and were shown to exist as a single contiguous sequence. This information supports the hypothesis that plasmid sequences have inserted into the chromosomal DNA and makes pEAS137 a good candidate for studying the relationships between the plasmids. Initial studies comparing pEAS137 to QpRS and QpH1 suggest that pEAS137 is more closely related to QpRS than to QpH1.
Savinelli
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EA
Department of Microbiology, Washington State University, Pullman 99164-4233.
Mallavia
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LP
D001483:Base Sequence; D002876:Chromosomes, Bacterial; D003381:Coxiella / Q000235:genetics*; D004697:Endocarditis, Bacterial / Q000209:etiology*; D006801:Humans; D010957:Plasmids; D011995:Recombination, Genetic; D012689:Sequence Homology, Nucleic Acid