Imagine diving into the ocean and witnessing a vibrant underwater world teeming with life. Brightly colored corals of various shapes stretch as far as the eye can see, home to countless marine creatures. These are coral reefs — the "rainforests of the sea" — occupying less than one percent of the ocean floor but supporting about 25 percent of all marine life. Coral reefs are the largest structures made by living organisms, visible even from space, yet their future is uncertain due to increasing environmental threats such as coastal development, global warming, overfishing, pollution, and more.

The Hidden Architects:

Coral Polyps: At the heart of coral reefs are tiny organisms called coral polyps. These jellyfish-like animals, ranging from millimeters to several centimeters in size, form colonies by a process called budding, where polyps create identical copies of themselves. Over time, these colonies grow and form the coral structures we recognize as reefs. The polyps secrete calcium carbonate (CaCO₃) exoskeletons that provide protection and give reefs their rigid structure.

Tentacles around each polyp's mouth allow it to capture small prey from the water. Although corals appear rooted like plants, they are part of the animal kingdom and rely on their partnership with algae for energy.

A Symbiotic Relationship:

The Key to Survival: Corals thrive due to their partnership with microscopic algae known as Symbiodiniaceae, which live inside the corals’ tissues. The algae use photosynthesis to provide the corals with energy and nutrients, also giving them their vibrant colors. In return, the algae receive shelter and access to carbon dioxide (CO₂). This symbiotic relationship is essential for coral survival.

However, when environmental stressors like rising sea temperatures occur, this partnership is disrupted.

Rising Temperatures and Coral Bleaching:

When ocean temperatures rise, Symbiodiniaceae produce reactive oxygen species (ROS), which can cause damage to coral tissues. In response, corals expel the algae, leading to coral bleaching — a process where corals lose their vibrant colors and become vulnerable to death. Without the algae, corals lose their primary source of energy, making them more susceptible to stress and disease.

In the most extreme cases, coral bleaching can lead to the death of entire reef ecosystems.

Coral Disease:

In addition to bleaching, corals are increasingly affected by diseases, which are correlated with rising temperatures. The prevalence of coral diseases has tripled over the past 25 years, and if temperatures continue to increase, it is predicted that over 76 percent of corals could contract diseases by the year 2100.

Why Should We Care?

Coral reefs are essential for the health of marine ecosystems, providing habitat for a wide variety of species, supporting fisheries, and protecting coastal areas from erosion. They are also an important economic resource, contributing to tourism and the livelihoods of millions of people around the world. The loss of coral reefs would have far-reaching consequences for both biodiversity and human economies.

A Synthetic Biology Solution:

The Reeform! Project:

Recognizing the urgency of protecting coral reefs, the NYU Abu Dhabi iGEM 2024 team has launched a project called Reeform. This project uses synthetic biology to enhance the resilience of corals to environmental stressors like heat and disease.

The team’s approach focuses on two key symbiotic partners of corals: Symbiodiniaceae and a beneficial bacterium called Endozoicomonas.

Engineering Symbiodiniaceae:

To help corals survive rising ocean temperatures, the team is working on enhancing the heat tolerance of Symbiodiniaceae. They plan to introduce genes that produce heat shock proteins (HSPs) and enzymes that can help the algae neutralize the harmful effects of ROS, improving the coral’s ability to cope with heat stress.

Enhancing Endozoicomonas:

Endozoicomonas is a bacterium found in healthy corals and plays a role in maintaining coral health. However, like the algae, Endozoicomonas populations decline under heat stress. The team aims to introduce genes that boost the resilience of these bacteria, allowing them to continue supporting coral health even as temperatures rise.

The Reeform! project focuses on engineering native coral symbionts, rather than introducing foreign species or performing microbiome transplants which can pose risks to the coral ecosystem. By strengthening the natural partners of corals, the team hopes to improve coral resilience while maintaining the balance of the reef ecosystem.

Progress and Challenges:

The NYU Abu Dhabi iGEM team is working to optimize the transformation protocols required to introduce genetic material into Symbiodiniaceae and Endozoicomonas. This includes building a genetic toolkit with regulatory elements that control gene expression in these organisms. While working with non-model organisms presents challenges, the team has made significant progress in culturing the organisms in the lab.

The project is an innovative attempt to address the threats faced by coral reefs. By focusing on strengthening the corals’ natural defenses through synthetic biology, the team aims to provide a potential solution to coral bleaching and disease, helping coral reefs survive and thrive in an increasingly challenging environment.