Publication Date

2016-5

Document Type

Honors Thesis

Department

Biological Sciences

Keywords

Genetic transformation, Filarial worms, Nematodes, Wolbachia, Endosymbiosis, Lateral gene transfer, Filarial nematodes, Mithionyl-tRNA synthetas, Porphobillinogen deaminase

Abstract

Filarial nematodes are parasitic worms that infect humans and animals alike, sometimes with severe consequences in health and the economy. Many such worms live in partnership with a bacterial endosymbiont, Wolbachia pipientis. Endosymbiotic Wolbachia are vital to the worms’ survival, as the bacteria carry out certain metabolic and reproductive functions. That is not the case for all filarial nematodes, however. Wolbachia-independent nematodes are able to survive on their own without an endosymbiont, but nonetheless still carry some Wolbachiaderived genes within their genome. This observation has been attributed to events of lateral gene transfer between Wolbachia and a common ancestor of Wolbachia-independent nematodes. The purpose of this project is to utilize a subset of Wolbachia-derived genes (PBGD, IspH and MetRS) to investigate the evolutionary history of lateral gene transfer between Wolbachia and filarial nematodes. Phylogenetic tree analysis of the PBDG genes shows that lateral gene transfer events succeeded the split between Wolbachia bacteria that live in nematodes versus arthropods. However, the size and diversity of the dataset are not large enough to draw any definitive conclusions. The MetRS gene was successfully sequenced in only one nematode species but showed a high degree of conservation to its Wolbachia homologs. Amplification of the IspH gene proved more successful, but PCR reaction parameters need to be adjusted to accommodate amplification in a larger variety of nematode species. The exact function of Wolbachia genes in Wolbachia-independent nematodes remains to be elucidated. Determining the degree of expression and conservation of such genes can aid us is designing drugs that target vital Wolbachia genes instead of the parasites themselves

Language

English

Comments

81 pages : illustrations (some color) Honors project, Smith College, 2016. Includes bibliographical references (pages 59-63)

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