VARIATION IN THE SIZE OF THE OSPA-CONTAINING LINEAR PLASMID, BUT NOT THE LINEAR CHROMOSOME, AMONG THE 3 BORRELIA SPECIES ASSOCIATED WITH LYME-DISEASE

The aetiological agents of Lyme disease form a phylogenetically hetero geneous group, composed of three species, Borrelia burgdorferi, Borrel ia garinii, and group VS461. We have compared the sizes of the linear plasmid that carries the genes encoding the major outer-surface protei ns OspA and OspB as well as the size and structure of the chromosome a mong the Lyme disease spirochaetes. We have found differences in the s izes of the ospA-containing plasmids, but not the linear chromosomes a mong the three species. The ospA-containing plasmid size of 50 kb in B . burgdorferi isolates is significantly smaller than the size of 55 kb in B. garinii isolates and 56 kb in group VS461 isolates. The chromos ome was found to be linear in all three Borrelia species. but not sign ificantly different in size.