CHANGES IN GUT MICROBIOME COMPOSITION FROM LOWER TERMITES IN RESPONSE TO ENVIRONMENTAL AND COLONY-GENETIC FACTORS
The relationship between termites and their gut microbiome is inseparable as the microbes provide plenty of physiological benefits such as digestion, acetogenesis, nitrogen fixation, caste differentiation and immunity. Therefore, it is very important to understand this relationship to attain innovations in pest management solutions. This project was undertaken to study the dynamics of termite gut microbiomes in response to environmental and colony-genetic factors. Here I investigated environmental variations under lab conditions by manipulating the social environment of termite workers via hormonal treatments (Chapter 2) and by exposing termites to commonly used insecticides (Appendix A). To investigate the interaction of gut microbes with natural environmental variation, I sampled field termites every month from May through October (Chapter 3). In addition, to study the impact of termite colony genetics, I reared termites originally from two different field colonies in a controlled environment in the lab (Chapter 4). The combination of lab and field investigations, and bioinformatic analyses have resulted in the following major findings- (1) gut microbes do impact the social environment within a colony, (2) seasonality has an impact on gut microbial abundances, (3) significant variation in microbiome follows genetics of termite colonies, and (4) insecticide applications do change the gut microbial loads specifically the protists load.
Results from these experiments support the idea that termite gut symbionts change their community structure possibly to help the host termite to be best fit to survive changing environmental conditions. For example, when termites were provided hormonal treatment to artificially induce caste differentiation, gut microbes were linked with this eusocial mechanism via differential selection. However, when termites were in the field experiencing change in the season, monthly temperature was correlated with several bacterial taxa, possibly selecting for taxa that help termite to thrive the changed environmental conditions. These results indicate that studying termite system without considering their gut microbiome would not provide a complete picture of physiological, biological or pest management studies. This dissertation altogether highlights the possible dynamics of gut microbiome to help a host adapt to changing conditions and emphasizes the importance of a holobiont approach while studying an insect system.
- Doctor of Philosophy
- West Lafayette