Evolutionary and Functional Studies of Wolbachia pipientis and its Phage

Wolbachia pipientis is an obligate intracellular bacterium of increasing importance in understanding the tripartite interactions between viruses, bacteria, and eukaryotes, as well as having applications in modern medicine in the fields of antibacterial therapy and disease vector biocontrol. Four studies were undertaken to examine various aspects of Wolbachia biology. In the first investigation, an analysis of the evolution, horizontal transfer, and antibacterial activity of a lysozyme gene encoded by Wolbachia’s bacteriophage WO was undertaken. This study showed that the lysozyme had transferred across the tree of life to confer antibacterial traits to species in all domains. Secondly, a Wolbachia strain causing multiple reproductive manipulation phenotypes in its insect hosts was sequenced and unexpectedly found to contain a number of phage WO genes that could be causal for these manipulations. Third, transgenic Drosophila melanogaster were generated expressing these genes and their ability to cause cytoplasmic incompatibility was tested, demonstrating for the first time that WO genes can alter arthropod reproduction. Finally, the mechanisms of Wolbachia adaptation to novel hosts were analyzed through genome sequencing and culture of Wolbachia in two different species, Drosophila melanogaster and Aedes aegypti. It was discovered that Wolbachia undergoes minimal genetic change but substantial phenotypic change after host switching. These studies further our understanding of Wolbachia interactions with virus and host and may enable future use of Wolbachia and WO genes as therapeutics or in pest control strategies.