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Title: A molecular study of the interactions between the parasitic nematode Brugia malayi and its endosymbiont, Wolbachia
Author: Fenn, Katelyn A.
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 2005
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The aim of this thesis is to work towards establishing the molecular basis of the communication between the host nematode Brugia malayi and its host specific Wolbachia strain, wBma. The genome sequence of wBma was annotated and compared to the published annotated genome of the Wolbachia found in Drosophila melanogaster (wMel). Interesting genes discovered in the wBma genome include a family of seven ankyrin repeat containing (ANK) proteins. ANK proteins are known to be involved in many protein:protein interactions, more commonly in eukaryotes. A comparison of the wBma ANK proteins with the 23 ANK proteins present in the genome of wMel shows that two of the wMel ANK homologues in the wBma genome are non-functional pseudogenes. wBma has novel ANK proteins that may be involved in interaction with the host cellular machinery. RT-PCR of the wBma ANK genes shows that different ANK genes are expressed in different stages of the nematodes’ life cycles. Many interesting Wolbachia novel genes were identified in the genome of wBma, wMel and the Wolbachia strain from the filarial nematode that causes river blindness, Onchocerca volvulus (wOvo). Novel proteins predicted to be located to the bacterial surface or predicted to be secreted are good candidates for proteins that may be involved in communication between Wolbachia and its host. A real-time PCR technique was developed to calculate the number of wBma per B. malayi nucleus at different stages in the nematodes’ life cycle. gDNA samples prepared from different stages of the life cycle showed that the number of wBma per nematode nucleus was observed to increase ten-fold during development from microfilaria (MF) to larval fourth stage (L4). Post-L4, while adult male somatic nuclei had approximately six-fold that of L4, the adult female soma is estimated to have approximately 330-fold more. If the Wolbachia were multiplying only to ensure its passage to the next generation of MF, there would be little obvious adaptive advantage in multiplication within the soma. However, if the Wolbachia are supplying some essential metabolic need to the nematode, then their multiplication in the soma will reflect the importance of their role at different lifecycle stages. This data suggests that wBma are supplying a possible essential role, but that role is yet to be identified. Another way that Wolbachia and its host may be interacting is by gene transfer from the bacteria into the nuclear genome of the host organism. The transfer of genes from prokaryote to eukaryote is still considered an unusual event, but there is evidence that genes have been transferred from organelles of prokaryotic endosymbionts origin, such as chloroplasts and mitochondria to the cell’s nuclear genome. This thesis has identified two wOvo pseudogenes in an untranscribed region of an O. volvulus nuclear gene.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available