Genetic Heterogeneity of Borrelia burgdorferi Sensu Lato in the Southern United States

Publication Year:
2000
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Repository URL:
https://digitalcommons.georgiasouthern.edu/etd_legacy/444
Author(s):
Lin, Tao
Tags:
ETD; Borrelia burgdorferi sensu lato; Strains; Ticks; Strain isolation; Biochemistry, Biophysics, and Structural Biology; Biology; Legacy ETDs
thesis / dissertation description
Fifty-nine strains of Borrelia burgdorferi sensu lato were identified and characterized with polymerase chain reaction (PCR) -restriction fragment length polymorphism (RFLP) of rrf-rrl intergenic spacer amplicons. PCR-RFLP results indicated that the strains represented at least 3 genospecies and 10 different restriction patterns. Most of the strains isolated from the tick Ixodes dentatus in Missouri and Georgia belonged to the genospecies Borrelia andersonii. Most strains isolated from the ticks Ixodes scapularis and Ixodes affinis, the cotton rat (Sigmodon hispidus) and cotton mouse (Peromyscus gossypinus), in Georgia, Florida, and Missouri, belonged to the genospecies Borrelia burgdorferi sensu stricto. Seven strains isolated from Ixodes minor, the eastern woodrat (Neotoma floridana), the cotton rat, and the cotton mouse in South Carolina and Florida, belonged to genospecies Borrelia bissettii. Strains MI-8 and TXW-1 exhibited different Mse I and Dra I restriction patterns from those of previously reported genospecies. The complete sequences of rrf-rrl intergenic spacers from 23 southeastern and Missouri strains were determined. Evolutionary and phylogenetic relationships of these strains were compared with other described genospecies. The 23 strains clustered into 5 separate lineages. Strains MI-8 and TXW-1 appeared to belong to 2 different undescribed genospecies. PCR-RFLP results and sequence analysis of the rrf-rrl intergenic spacer confirm that greater genetic heterogeneity exists among Borrelia burgdorfen sensu lato strains isolated from the southern compared to those from the northern U.S.A.The ospC genes of twenty-three southern strains were amplified. A similarity matrix based on amino acid sequences indicated that a high degree of similarity exists between Borrelia burgdorferi sensu stricto and Borrelia bissettii, and between Borrelia bissettii and Borrelia andersonii, and that the three genospecies are closely related. The highest degree of genetic diversity among them was observed in the two variable domains (V1 and V2), semivariable domain (SV), and the species-specific epitopes (between aa 28 and aa 31). Compared to European Borrelia burgdorferi sensu stricto strains, American Borrelia burgdorferi sensu stricto strains show greater genetic heterogeneity. Moreover, greater genetic diversity exists among southern Borrelia burgdorferi strains than northern strains.The ospC genes of twenty-three southern strains were amplified. A similarity matrix based on amino acid sequences indicated that a high degree of similarity exists between Borrelia burgdorferi sensu stricto and Borrelia bissettii, and between Borrelia bissettii and Borrelia andersonii, and that the three genospecies are closely related. The highest degree of genetic diversity among them was observed in the two variable domains (V1 and V2), semivariable domain (SV), and the species-specific epitopes (between aa 28 and aa 31). Compared to European Borrelia burgdorferi sensu stricto strains, American Borrelia burgdorferi sensu stricto strains show greater genetic heterogeneity. Moreover, greater genetic diversity exists among southern Borrelia burgdorferi strains than northern strains.