The molecular biology of Borrelia.
Borrelia burgdorferi, the cause of Lyme disease, has two major outer-membrane proteins, OspA and OspB, which act as surface antigens. A 49-kilobase linear plasmid contains the genes that encode for these surface proteins. Direct examination of denatured plasmid molecules has revealed single-stranded circles with a circumference of approximately 100 kilobases (about twice the length of the linear duplex molecule), a finding that indicates the plasmid strands have covalently closed ends. This form of DNA, while present in eukaryotic organisms and their viruses, has not been observed in a prokaryotic organism. Plasmid heterogeneity has been observed in strains with surface proteins of similar molecular weights and similar monoclonal antibody reactivity. Thus, plasmid analysis may prove a sensitive tool for differentiating strains of B. burgdorferi. Furthermore, since loss of plasmids in vitro has been correlated with loss of the ability of many-passaged strains to cause infection, borrelial plasmids may encode for virulence factors as well.
Barbour
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Department of Medicine, University of Texas Health Science Center, San Antonio, Texas 78284.
D000818:Animals; D000942:Antigens, Bacterial / Q000235:genetics*; D000954:Antigens, Surface / Q000235:genetics; D001425:Bacterial Outer Membrane Proteins / Q000235:genetics*; D001898:Borrelia / Q000235:genetics* / Q000276:immunology; D003001:Cloning, Molecular; D004269:DNA, Bacterial / Q000032:analysis* / Q000648:ultrastructure; D006801:Humans; D010957:Plasmids
D000942:Antigens, Bacterial; D000954:Antigens, Surface; D001425:Bacterial Outer Membrane Proteins; D004269:DNA, Bacterial