Plasmid DNA Sequence Analysis Elucidates Evolution of Species-Specific Tsetse Fly Symbiotic Bacteria

Noah J. Spencer*, Miguel E. Medina Muñoz, Rita V.M. Rio, Department of Biology, West Virginia University, Morgantown, WV 26505

Field (Broad Category): Biology (Biological & Biochemical Sciences) 

Student’s Major: Biology 

Tsetse flies, blood-feeding insects that transmit the deadly parasite Trypanosoma bruceii, rely on the specialized bacterium Wigglesworthia glossinidia to survive on their strict blood diet. These bacteria live exclusively within the tsetse fly and are transmitted from parent to offspring each time the fly reproduces. This strict association has led to irreversible shrinking of the Wigglesworthia genome, making it streamlined for symbiosis. Genome sequencing of Wigglesworthia isolates from two distantly related tsetse species, Glossina morsitans and Glossina brevipalpis revealed that, despite evolving in separate host fly lineages for millions of years, they shared a roughly 5kb plasmid (extrachromosomal DNA) encoding several known stress response genes. This conservation suggested a potential function of these genes towards symbiosis. However, quantification of Wigglesworthia plasmid sequences in G. morsitans revealed that it was present in low copy numbers, suggesting that the plasmid structure itself may not be adaptive and could be lost in other lineages. Genome sequencing of Wigglesworthia symbionts from additional tsetse species will reveal the patterns of this genomic feature’s evolution, highlighting trends in the evolution of highly reduced genomes and potentially elucidating differences in the capacity of different tsetse species to transmit trypanosomes. Here, we report on novel sequencing results for the Wigglesworthia symbiont of the tsetse fly species Glossina palpalis gambiensis with a focus on the evolution of the Wigglesworthia plasmid and associated genes. 

Funding: National Institutes of Health 

Program/mechanism supporting research/creative efforts: Biology 486 capstone