CHARACTERIZATION OF CP18, A NATURALLY TRUNCATED MEMBER OF THE CP32 FAMILY OF BORRELIA-BURGDORFERI PLASMIDS

We have mapped the genes encoding the antigenic lipoproteins OspE and OspF to an approximately 18-kb circular plasmid in Borrelia burgdorfer i N40. Sequencing and restriction mapping have revealed that this plas mid, cp18, is homologous to an 18-kb region of the cp32 circular plasm ids found in the Lyme disease spirochetes. Our data show that cp18 may have arisen from an ancestral cp32 plasmid by deletion of a 14-kb reg ion of DNA, indicating that a significant portion of the cp32 plasmid is not essential in cis for plasmid maintenance. These findings sugges t that a relatively small recombinant plasmid capable of being stably maintained in B. burgdorferi could be constructed from a cp32 plasmid.