Characterization of Circular Plasmid Dimers in Borrelia burgdorferi |
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| Authors: | Kit Tilly Lori Lubke and Patricia Rosa |
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| Institution: | Laboratory of Microbial Structure and Function1. and Microscopy Branch,2. Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, Hamilton, Montana 59840 |
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| Abstract: | We have inactivated the ospC, oppAIV, and guaB genes on the 26-kb circular plasmid of Borrelia burgdorferi (cp26) by allelic exchange. On several occasions following such transformations, the cp26 of transformants had an aberrant mobility through agarose gels. Characterization of these cp26 molecules showed that the plasmid had dimerized. These dimers were quite stable during either selective or nonselective passage. Subsequent transformations with dimer DNA supported the hypothesis that in B. burgdorferi, transforming cp26 DNA most likely does not displace the resident homologous plasmid but rather must recombine in order to donate sequences that it carries. These serendipitous findings provide a mechanism for obtaining heterozygous complemented control strains when mutant phenotypes are characterized. |
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