Every ecosystem on our planet is composed of a complex community of organisms. Life in these ecosystems is often dependent on mutually beneficial interactions between community members. Syntrophy is a type of metabolic cooperation used by microorganisms where nutrients are exchanged between individuals to allow for metabolic division of labor. Such interactions are common between prokaryotic organisms, especially in low oxygen zones (e.g. aquatic sediments, gastrointestinal tract) where suitable terminal electron acceptors are rare. As ‘aerobes’, when we metabolize sugars, we release electrons that are ultimately transferred to oxygen which serves as the ‘electron sink’. In contrast, some anaerobes do not require oxygen but instead have complementary physiology with other organisms whereby the metabolism of one partner can serve as the ‘electron sink’ of the other. These relationships are key to environmental biogeochemical functions, agriculture, bioelectricity generation and were likely instrumental in the evolution of eukaryotic cell. Establishing such relationships can have major biological consequences to the partners, e.g.,: syntrophy allows organisms to persist in a new environment that could not be accessed individually and syntrophy can become obligatory leading to the evolution of new lineages shaped by co-evolution of the host and symbiont. A lot of what we know about syntrophic interactions and their evolutionary implications stems from studies of prokaryotes where numerous examples have been characterized. Whether syntrophic interactions have been a major force in the evolution eukaryotic microbes remains largely unexplored. We understand very little about nature of syntrophic relationships between eukaryotes and other organisms in OMZs, yet such environments are key to many environmental functions (e.g. carbon, nitrogen and sulfur cycles), livestock rearing (e.g. animal gut health), and human gut health and are therefore worthy of study.
The goal of this proposal is to advance our fundamental knowledge of the diversity, molecular mechanisms, and evolutionary history of syntrophy in eukaryotes by studying the eukaryotic lineage Breviatea. This will be accomplished by: 1) developing a model system to decode the partner recognition and molecular mechanisms that dictate syntrophic interactions in breviate protists 2) expanding the known genomic diversity and symbiotic potential of the Breviatae lineage and 3) Objective investigate breviate:prokaryote symbioses in the natural world using cultivation-independent methods.
