Doctor of Philosophy (PhD)
The Formosan subterranean termite (FST), Coptotermes formosanus, is an invasive urban pest in the United States. Colonies of the FST are dependent on the symbiotic gut protozoa for cellulose digestion in the workers’ guts, and the gut bacterial community is known to provide essential nutrients to the termite. The objectives of this PhD research were to develop and evaluate paratransgenesis and phage therapy for termite control. During this study, a termite gut bacterium: Trabulsiella odontotermitis was genetically engineered and was evaluated as a ‘Trojan horse’ for paratransgenesis. We proved that T. odontotermitis can tolerate 50 times more concentration of ligand-Hecate than the concentration required to kill the gut protozoa. We also engineered T. odontotermitis to express Green Fluorescent Protein (GFP) and visualized the expression of GFP in the termite gut. We created a strain of T. odontotermitis expressing kanamycin-resistant gene using tn7 transposon. We used this strain to prove that once ingested, T. odontotermitis can stay in the termite gut for at least three weeks and it is horizontally transferred amongst nest mates. We also engineered T. odontotermitis to express functional ligand-Hecate-GFP fusion protein. Removal of the bacterial community from the gut also has a negative impact on the survival of the termites. The presence of a diverse and rich bacterial community makes the termite gut a perfect niche for bacteriophages; viruses that infect bacteria. So far, there has been no research to study the presence and role of bacteriophages in the gut of the termite. Bacteriophages have the potential to be used in ‘Phage therapy’ targeting the essential termite gut bacteria. During this study three novel bacteriophages were isolated and sequenced from the termite gut. A meta-virome sequencing of the termite gut was also done, which revealed the presence of previously unknown bacteriophages and other viruses associated with the termites. This is the first study elucidating the presence of a diverse and largely unexplored bacteriophage community in the termite gut. The study suggests that termites can serve as a model system to study the effect of bacteriophages on bacteria and ultimately on the host harboring the microbial community.
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Tikhe, Chinmay Vijay, "Termite Gut Microbes as Tools and Targets for Termite Control" (2017). LSU Doctoral Dissertations. 4393.