Coral reefs are intricate ecosystems with complex relationships between species, where each organism—from a tiny bacterium to a giant clam—plays a vital role in maintaining the health of the reef.
Coral reefs are intricate ecosystems with complex relationships between species, where each organism—from a tiny bacterium to a giant clam—plays a vital role in maintaining the health of the reef.
Our new study reveals yet another layer of complexity in coral reefs.
We discovered the presence of clusters of two kinds of bacteria inside the tissues of corals, which included, oddly, a close relative of the chlamydia-causing bacteria.
These novel findings, published in Science Advances, indicate that these bacteria may interact both with their coral host and with each other. Further work is required to understand whether these interactions are beneficial or harmful to the coral.
Just like humans, corals have a diverse bacterial microbiome that is tightly linked to their health. So, understanding the complex relationships between coral and bacteria is critical for understanding how corals function.
Credit: University of Melbourne
Bacteria can help corals with several biological processes, like nitrogen or sulfur movement and processing, or the production of antibacterial compounds that protect corals against pathogens. While most of these bacteria live in the mucus layer that covers the coral surface, some bacteria occur inside the coral tissues.
Very little information is available on tissue-associated bacteria, yet they are likely some of the most important members of the coral microbiome.
To find out more, samples were taken from a long-term experiment on the Great Barrier Reef coral species Pocillopora acuta carried out at the Townsville-based Australian Institute of Marine Science. These samples were shipped to our laboratory at the University of Melbourne to investigate the elusive tissue-associated bacteria.
The first challenge was to see the bacteria—they are very small.
