Genetic diversity among Borrelia burgdorferi isolates: more than three genospecies?

In order to assess the genetic relationships among isolates of Borrelia burgdorferi, we have determined chromosomal DNA restriction fragment length polymorphisms (RFLP) of 27 isolates. Using five restriction enzymes and seven DNA probes, we recorded 246 different hybridizing bands. The resulting matrix was subjected to factorial correspondence analysis and to phylogenetic analysis using a parsimony program. These analyses demonstrate two closely related genospecies and three individual strains. RFLP variations among these three strains are much more pronounced than among the members of the other two genospecies. This may indicate the existence of more than three genospecies. Plasmid analysis did not contribute significantly to the genotypic differentiation.