A system for site-specific genetic manipulation of the relapsing fever spirochete Borrelia hermsii.

The lack of a system for genetic manipulation has hindered studies on the molecular pathogenesis of relapsing fever Borrelia. The focus of this chapter is to describe selectable markers, manipulation strategies, and methods to electro-transform and clone wild-type infectious Borrelia hermsii. Preliminary studies suggest that the variable tick protein (Vtp) of B. hermsii is involved in tick-to-mammal transmission. To address this hypothesis, we have developed a system for genetic manipulation and have constructed clones of a Vtp mutant and an isogenic reconstituted strain. The methods described here are applicable for the inactivation of other loci in B. hermsii and should be adaptable for other species of relapsing fever spirochetes.