Metabolic investigation of chemoheterotrophic endosymbionts of gutless oligochaetes

The concept of a nested ecosystem and the interchanges among biotic and abiotic factors is one lens through which we can approach the study of the specific associations between organisms that live closely together known as symbioses. The work presented herein builds upon the foundational works on the chemotrophic symbiosis between marine gutless oligochaetes and their various chemoautotrophic and chemoheterotrophic symbionts. To expand on the previously observed taxonomic and metabolic diversity of these symbiotic associations, I focused the work of my dissertation on two of the chemoheterotrophic phyla that occur in various permutations in this symbiosis – Desulfobacterota and Spirochaetota. I provided new insights into the ecology and heterotrophic niche partitioning in these microbiomes, determined metabolic mechanisms that allow for carbon and energy conservation in a symbiotic lifestyle, and optimized a method that leaves room to continue these metabolic explorations in future studies of this and other symbioses.