Assessing microbe mediated adaptation to different food sources via comparative symbiomics of lower termites
Final Report Abstract
Animals live in a microbial world. The interactions of animals with microbes span the parasitismmutualism-continuum and microbes are possibly the most important drivers of evolution. Genes that are involved in pathogen defense often evolve rapidly, and on the other hand microbes can be important facilitators of adaptation for higher organisms. In this project we worked with a text book example of adaptation via symbiosis: lower termites and their gut symbionts that faciliated living on a wood based diet. We set out to better understand (i) if and how the termite gut microbiome might contribute to adaptation to different life styles and diets and (ii) if and how the termite host chooses its microbial patners. We found pervasive evidence of ecology related changes in microbiome composition and function. We pinpointed microbial species and metabolic pathways that likely contribute to adaptation. We discovered that the foraging species have a much higher metagenomic potential to utilize nitrate as a nitrogen source than the wood-dwelling species. Nitrogen is a growth limiting resource for termites because wood is nitrogen-poor. Nitrate is common in soil which is accessible for the foragers, but not for the wood-dwellers. Therefore, the additional potential to use nitrate as a resource in foragers is very likely an adaptation to foraging. Furthermore, we have preliminary results from an experiment where we first removed the gut microbiome and then recolonized the termites. Only the foraging species activates specific genes during the recolonization process, while the wood dwelling species that we analyzed did not. This might point towards a more specific selection process of the microbial partner in the gut of foraging species that encounter a much broader microbial diversity. Finally, we analyzed a comprehensive set of immune genes for signals of increased or relaxed selection that would depend on ecology in a comparative genomics approach. We found no evidence for ecology related changes in selective pressure on the single copy ortholog immune that we investigated. During the course of the project we developed a new set of primers that lifted the metagenetic analysis of the termite parabasalid community into the illumina sequencing age, thus creating an important resource for the community. Furthermore, by performing the first experiment under controlled conditions in the laboratory, we set new standards in termite microbiome research that allowed us to disentangle the evolved microbiome from transient microbes and address evolutionary questions. Taken together our work set important new impulses for understanding the role of the microbiome in adaptation.
Publications
- (2017). Differential Ecological Specificity of Protist and Bacterial Microbiomes across a Set of Termite Species. Front. Microbiol. 8
Waidele, L, Korb, J, Voolstra, CR, Künzel, S, Dedeine, F, and Staubach, F
(See online at https://doi.org/10.3389/fmicb.2017.02518) - (2019). Ecological specificity of the metagenome in a set of lower termite species supports contribution of the microbiome to adaptation of the host. Animal Microbiome
Waidele L, Korb J, Voolstra CR, Dedeine F, Staubach F
(See online at https://doi.org/10.1101/526038) - (2019). No evidence for immune-gene specific signals of selection in termites
Meusemann K, Korb J, Schughart M, Staubach, F
(See online at https://doi.org/10.1101/783738)
