Term of Award

Summer 2003

Degree Name

Master of Science

Document Type and Release Option

Thesis (open access)


Department of Biology

Committee Chair

Frank E. French

Committee Member 1

Laura B. Regassa

Committee Member 2

William Irby


Spiroplasma bacteria (Mollicutes: Spiroplasmataceae) are characterized by motility, helical morphology and are most frequently found in insect guts and phloem tubes of plants. Traditionally, Spiroplasma have been classified by serology. Recent work has generated 16S rDNA sequences that generally correlate with the serological findings. Although the serology and the 16S rDNA sequence analysis clearly classifies strains to the group level, they do not distinguish between strains within the same group. The goal of this project was to investigate the utility of the 16S-23S rDNA intergenic spacer region sequence as a means to distinguish these closely related strains.

We chose Group VIII strains for this analysis because they were not separated by 16S rDNA analysis. We generated 16S-23S rDNA intergenic sequence and detailed serological profiles for eight Group VIII spiroplasmas isolated from North American and Australian horse flies. Within 293 nucleotides of 16S-23S rDNA intergenic spacer region, there was 96% identity among the eight strains. The sequence analysis grouped the strains into 3 main clusters, with the type strains Spiroplasma chrysopicola, S. syrphidicola, and TAAS-1 and BARC2649 each falling in to a different cluster. The phylogenetic analysis did not correlate precisely with the detailed serology. In addition, the phylogenetic groups did not correspond with geographic or host diversity.


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