How Coral’s Bacterial Partners Shield Reefs from Heat
New research from NYU Abu Dhabi reveals an elegant symbiosis: bacteria living within corals produce steroid hormones that bolster the reef's immune defences when temperatures surge, offering fresh insight into nature's resilience mechanisms.
In the warm waters near Saadiyat Island, coral colonies harbour an invisible ally. A groundbreaking study from New York University Abu Dhabi has illuminated how bacteria living within these ancient organisms produce steroid hormones—testosterone and progesterone among them—that act as biochemical guardians when heat stress threatens survival.
The research, published in Nature Microbiology, focused on Acropora pharaonis corals from the Arabian Gulf and centred on a bacterium called Endozoicomonas, which exists in symbiosis with coral species across the world. When water temperatures rise, the coral’s own capacity to manufacture the steroid hormones vital for immune regulation diminishes. Yet its bacterial partners respond to this stress by synthesising these molecules themselves, effectively compensating for the host’s shortfall and enabling the coral to mount a fortified immune response.
“When temperatures become high, corals lose some of their ability to produce steroid hormones that are important for regulating their immune system,” explained Amin Mohamed, Research Associate at NYUAD and first author of the study. “We found that their bacterial partners can compensate by producing these hormones themselves, allowing the coral to activate an immune response that helps its cells survive the heat.”
The discovery reveals a previously unknown dimension of the coral microbiome’s function. Steroid hormone production has long been considered the province of complex organisms, with only a small number of bacterial species previously documented to manufacture these molecules, notably certain strains found in the human gut. That coral-associated bacteria possess this capability speaks to the sophistication of microbial biology and the intricacy of host and microbe relationships.
“These bacteria are doing much more than simply living alongside the coral,” said Shady Amin, Associate Professor of Biology at NYUAD and senior author of the study. “They are providing the coral with molecules it needs to regulate its immune response at a time when the coral itself is under significant stress.”
The implications for coral conservation extend beyond the laboratory. While existing efforts such as coral nurseries, restoration programmes, and assisted evolution focus predominantly on enhancing the coral organism itself, this research opens a novel avenue: leveraging the beneficial functions of coral-associated microorganisms to strengthen resilience against environmental pressures. The work was undertaken through NYU Abu Dhabi’s Centre for Genomics and Systems Biology.
What it means for Abu Dhabi
The Arabian Gulf presents one of the world’s most challenging environments for coral survival, with temperature fluctuations that test the limits of reef resilience. This research, grounded in the study of locally sourced Acropora pharaonis corals, provides Abu Dhabi and the broader region with deeper understanding of the mechanisms sustaining these vital ecosystems. The findings illuminate why certain coral populations persist in the Gulf’s demanding waters and suggest that microbial enhancement could complement existing conservation strategies being pursued across the Emirates.
As global temperatures continue to shift, the knowledge that bacterial partners contribute actively to coral survival offers encouragement for conservation efforts. For Abu Dhabi, where coral reefs support both marine biodiversity and the cultural and economic value of the coastline, this science reinforces the interconnectedness of all life systems and underscores the importance of protecting the microbial communities that sustain the reef.
Source: WAM