BRC-BIO:The symbionts' symbionts: Dissecting the microbiome of the coral endosymbiont (Symbiodiniaceae)

American University, Washington DC

Investigators

Abstract

Coral reefs are among the most biodiverse ecosystems on Earth, yet they are increasingly threatened. At the heart of coral reef health lies the symbiosis between corals and photosynthetic microalgae that provide essential nutrients to their hosts. This partnership underpins coral reef productivity and resilience, but rising ocean temperatures are causing widespread coral bleaching, driven by the breakdown of this symbiosis. Understanding the factors that influence coral thermal tolerance is critical for protecting reefs, and while algal diversity plays a key role, the potential contributions of their associated bacterial communities remain underexplored. Recent findings suggest that bacteria residing within the specialized cell compartment housing microalgae may influence microalgal functioning, opening new avenues for research into enhancing coral resilience. This project investigates the diversity, functional roles, and potential applications of microalgal-associated microbiomes, aiming to uncover strategies for mitigating the impacts of ocean warming on coral reefs. The project will train many students, equipping them with skills highly sought after in both academic and industrial settings. By fostering a new generation of scientists and advancing our understanding of coral resilience, this work will contribute to the preservation of coral reef ecosystems and their vital ecological and societal benefits. This research will provide a comprehensive analysis of Symbiodiniaceae (i.e. microalgae symbiotically associated with corals) microbiomes freshly extracted from corals, using a combination of amplicon and metagenomic sequencing to characterize their taxonomic and functional diversity across five coral species from Florida's Coral Reef. The project will isolate bacterial strains from these microbiomes and assess their effects on Symbiodiniaceae physiology through contact-independent co-culture experiments and transcriptomic analyses, identifying molecular mechanisms underlying these interactions. Finally, bacterial strains capable of enhancing Symbiodiniaceae photosynthetic efficiency will be tested for their ability to improve algal thermal tolerance. These findings will provide novel insights into the organizational complexity of coral holobionts and their adaptive potential in a warming ocean, laying the groundwork for microbiome-based interventions to support coral restoration efforts. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.