Study reveals untapped potential of coral reefs as nature’s pharmacy

SINGAPORE – A study has uncovered hundreds of new microbial species inhabiting coral reefs, a discovery which may one day prove invaluable in helping save lives.

Researchers at Swiss university ETH Zurich analysed the microbiomes of reef-building corals and found that an overwhelming majority of microbial species identified had no previous genomic information known to science.

Reef-building corals refer to corals that produce a rigid skeleton made of calcium carbonate, such as stony corals.

The study, published in science journal Nature on Feb 25, found that these micro-organisms also produced novel enzymes and molecules, which may potentially contribute to the development of medicine and pharmaceuticals.

This discovery not only reveals the untapped potential of coral reefs for biomedical and biotechnological breakthroughs, but also provides additional economic and scientific incentive to boost global conservation efforts, said Professor Shinichi Sunagawa, who specialises in microbiome research at ETH Zurich.

“Our research proves that protecting coral reefs isn’t just about saving the visible animals; it’s about preserving an irreplaceable library of molecular diversity,” Prof Sunagawa, one of the lead researchers, told The Straits Times.  

Coral microbiomes – which are made up of tiny living micro-organisms such as bacteria and algae – provide corals with vital nutrients and vitamins. These microscopic communities, which are highly specific to their host coral, can also protect corals from infectious diseases and help them cope with changing environmental conditions such as warming waters.

From 2016 to 2018, ETH researchers visited 32 islands across the Pacific Ocean, where trained divers collected coral samples from 99 reefs. The research was done in collaboration with researchers from the Swiss Federal Technology Institute of Lausanne and the Tara Ocean Foundation, a French foundation dedicated to marine research.

The samples were then taken to a lab in France, where researchers reconstructed and analysed the genome sequences of the micro-organisms. They also analysed data from other reef microbiome studies to identify the extent of differences between the microbiome of corals and that of sponges and reef water. 

After analysing 820 samples, researchers reconstructed the genomes of 645 microbial species inhabiting the corals, with more than 99 per cent of them being new to science. The findings also revealed that more micro-organisms which produce organic compounds were found in the reefs than in the open ocean. 

Some of these micro-organisms were found to have unique characteristics, such as a strain of bacteria called Acidobacteria, which was observed to display unusual enzymatic activity – the ability of enzymes to catalyse a biochemical reaction. The genomes of such microbes may be of interest for biotechnology applications, said Prof Sunagawa.

While coral microbiomes have been closely studied, uncovering the information encoded by the genomes of micro-organisms has been technically challenging and cost-intensive, resulting in a lack of knowledge about what the microbes can do, he said. 

However, microbes with the ability to produce natural substances such as anti-inflammatory and anti-tumour agents have previously been discovered on other reef organisms such as sponges and soft corals. 

This inspired the team to look into whether reef-building corals also harboured microbes with the genetic capacity to produce such substances, he explained. 

As the study focused only on samples from three types of corals – stony, fire and soft corals – among hundreds of coral genera, there remains many more microscopic secrets to be uncovered, said Prof Sunagawa. “The microbiomes of many diverse marine groups, such as sponges and algae, are also still insufficiently researched,” he added. “Preliminary analyses show that we have only scratched the surface, and that there is an enormous amount of undiscovered microbial life out there in the reefs of our planet.”

To close the massive knowledge gap regarding unknown microbial species associated with corals and other reef-inhabiting organisms such as sponges, researchers will be embarking on a new expedition called Tara Coral in 2026.

However, researchers are also working against warming ocean waters and emerging diseases which threaten coral reefs. 

As these micro-organisms are closely associated with their host, the impact of biodiversity loss in coral reefs is multiplied exponentially, said Prof Sunagawa.  

He added: “While it is incredibly exciting to discover that the molecular exploration of coral reefs holds such enormous discovery potential, the extent to which these ecosystems are unknown is deeply concerning.”

He noted: “We are under intense time pressure to unlock and protect this potential before these ecosystems reach an irreversible tipping point. 

“If we lose the reefs, we don’t just lose the corals – we lose this vast molecular reservoir before we even have the chance to understand or utilise it.”

Marine biologist Huang Danwei, deputy head of the National University of Singapore’s Lee Kong Chian Natural History Museum, said that the finding of new microbial species unknown to science was striking, especially given that corals and their microbial associates have been studied for decades.

Associate Professor Huang, who was not involved in the study, told ST that the possibility of corals harbouring organic compounds that can play a role in medical treatment should provide added motivation to conserve corals in South-east Asia. 

Singapore sits near the Coral Triangle, one of the most biodiverse marine areas in the world spanning the waters of Malaysia, Indonesia, the Philippines, Papua New Guinea, Timor-Leste and the Solomon Islands. 

“South-east Asia’s reefs are a global biodiversity hot spot, providing nursery habitats hosting diverse fish communities and maintaining ecosystem stability,” said Prof Huang. “They are also critical for the region because they provide benefits such as food security, livelihoods and coastal protection.” 

He added that there are ongoing local projects focused on building microbial communities to support coral resilience, which can help to raise the thermal tolerance of corals and boost their performance during marine heatwaves.

“Given that South-east Asia sits in the most diverse marine region of the world, many more currently unknown genomic and biosynthetic functions are awaiting discovery and application,” he said.