ANALYSIS AND COMPARISON OF PLASMID PROFILES OF BORRELIA-BURGDORFERI SENSU LATE STRAINS

The relationship between plasmid profiles and genospecies of the Lyme disease borreliae was investigated by using 40 strains from diverse bi ological and geographical sources, The genospecies of the strains were determined by examination of rRNA gene restriction patterns with cDNA probes complementary to the 16S and 23S rRNAs of Escherichia coli, Pl asmid profiles were obtained by pulsed-field gel electrophoresis, The number of plasmids per strain and the size of these plasmids ranged fr om 4 to 10 and from 13.3 to 57.7 kb, respectively, The strains all con tained a single large plasmid of 50 to 57.7 kb, with the exception of two Borrelia garinii strains that contained two or three of the large plasmids, The large plasmids of Borrelia burgdorferi sensu stricto str ains ranged in size from 51.4 to 52.7 kb and were consistently smaller than the 54.0- to 57.7-kb plasmids present in B. garinii and Borrelia afzelii. The exceptions to this observation were the two B. garinii s trains with multiple large plasmids; in this case the large plasmids w ere 50.6 to 53 kb. Although a large degree of heterogeneity in the siz es and frequencies of occurrence of smaller plasmids was observed, the re were some differences among the three genospecies. The differences in plasmids were further studied by using two Bam HI DNA fragments fro m a 28.7-kb plasmid of B. burgdorferi sensu stricto 297 as probes, Bot h probes hybridized with the 27- to 29-kb plasmids of B, burgdorferi s ensu stricto strains. In contrast, two patterns of hybridization were observed with B. garinii and B. afzelii. One pattern was the hybridiza tion of both probes, with each probe hybridizing with a different plas mid. The other pattern was the hybridization of a plasmid of a strain with only one of the two probes. Some strains of the three genospecies did not hybridize with either probe, Our results suggest that the pla smid profiles of B. burgdorferi sensu late have genospecies characteri stics and that the hybridization patterns of similar-sized plasmids ar e different for the three genospecies.