Elucidating the nature of the symbiosis between reef-building corals and common Endozoicomonas bacteria

Coral reefs are economically important ecosystems that provide jobs and coastal protection services to over a billion people worldwide. Corals are under threat worldwide from anthropogenic disturbances and climate change, and enhanced knowledge of their biology and health is needed for conservation and restoration solutions. This project will pursue research on a common coral-bacterial relationship with the overall goal of understanding the nature of this symbiosis and to determine if the bacteria provide growth or resilience benefits to the coral. Enhancing coral-bacterial symbiosis knowledge will facilitate more informed decisions about microbial-based interventions in coral health, including probiotics and disease treatments. This project will produce novel data which will advance understanding of coral-bacterial relationships and interactions. The researchers will focus work on corals located on economically important reefs located within the U.S. territory of the Virgin Islands. The knowledge gained will be broadly shared by engaging audiences in appropriate formats, including graduate student education and training of undergraduate students. Outreach to middle and high school students will occur in collaboration with a U.S. Virgin Island summer camp. Symbiosis-based lessons will also be presented to to pre-K and elementary school audiences, and a science café style event for all ages. Project findings will be shared through publicly through open access manuscripts and accessible press releases and social media posts. Bacteria belonging to the gammaproteobacterial genus Endozoicomonas are abundantly associated with diverse species of worldwide corals which form the framework supporting biodiverse and economically important reef ecosystems. It is unknown whether these enigmatic symbionts, which often form aggregates within coral tissues, provide benefits or detriments to corals. This project seeks to to understand the relationship between Endozoicomonas and the coral holobiont. Leveraging the Caribbean coral Porites astreoides which naturally occurs on reefs with and without prominent Endozoicomonas symbionts, the investigators will perform a series of field and aquaria experiments and employ a variety of sequencing, stable isotope, visualization and mass spectrometry-based methodologies to examine growth, immune defense and nutrition-based impacts of Endozoicomonas on the coral holobiont. Specifically, this proposal will examine the following aims: 1) Coral Growth - determine if the presence of Endozoicomonas symbionts infers growth benefits to the coral, 2) Immune Defenses - understand if the presence of Endozoicomonas symbionts influences disease onset or resistance in corals and 3) Nutrition - examine if Endozoicomonas symbionts show evidence of nutritional and metabolic interactions with the coral holobiont. Understanding coral-Endozoicomonas interactions will fill a key knowledge gap in the systems biology of corals that may be directly useful for designing coral intervention strategies. 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.