Molecular Characterization of Borrelia burgdorferi Linear Plasmids by DNA Hybridization, PCR, Two-Dimensional Gel Electrophoresis, and Electron Microscopy

Borrelia burgdorferi sensu stricto is the predominant cause of Lyme disease. B. burgdorferi strains carry several linear and circular plasmids and this may be also used as a distinguishing property of the bacteria. The presence of a mixed population oflinear and circular plasmids makes separation and characterization of each kind very difficult. In this study, 7 clinical strains of skin and CSF isolates were determined by clonal selection and plasmid profile of B. burgdorferi by electron microscopy and 2-dimension alagarose gel electrophoresis. The results demonstrate that the skin isolate (DK1) has 2 different phenotypes A and B, but the CSFisolate (DK6) has only 1 phenotype. Plasmid profiles from different strains of B. burgdorferi showed extreme complexity analyzed by conventional agarose electrophoresis. In conclusion, the DK1 strain has 10 plasmids in comparison to 6 plasmids in the DK6 strain. This could be due to a mixture of 2 phenotypes in the DK1 strain. Most of the plasmids in both strains were linear. This conclusion is supported by DNA hybridization, electron microscopy of plasmids, and amplification experiments with OspA-B specificprimers.