These preliminary results were presented this month at the 12th International Coral Reef Symposium in Cairns, Australia (ICRS), which included participants from about 80 countries and is held every four years to advance scientific knowledge, conservation, and management of coral reefs.
This ongoing study is a key advance in understanding the processes underlying coral reef growth and health. Reefs depend on intricate relationships between corals and many marine microscopic life forms, including the symbiotic algae within coral tissues and beneficial bacteria living on and near the reef. Most of these relationships are still being described by researchers.
Scientists have long known that bacteria — most of which reproduce by splitting rather than sex— are also able to transfer genes from one to another through something called “horizontal gene transfer.” One way bacteria do this is by producing particles called “gene transfer agents” (GTAs). In this process, random pieces of a donor bacterium’s DNA are packed into GTAs — packets containing pieces of DNA called genes — and released. Once set free, like genetic escape pods, these GTAs act like viruses “infecting” other bacteria and spreading the donor’s DNA fragments throughout the microbial community.
Researchers suspect that sharing GTAs could allow bacteria to spread beneficial genes across reefs, possibly helping corals, their resident algae or fellow reef-dwelling bacteria adapt to environmental challenges quickly. Sharing GTAs can take minutes, whereas adapting by traditional evolution can take thousands of years.
Scientists at KAUST are working to describe the gene-sharing process in detail. The DNA of a widespread marine bacteria called Ruegeria appears to have its strongest effect on the bacteria, algae or other microbes in the biofilm, helping them grow, multiply, produce substances or do other activities that help provide a better “landing pad” for the coral larvae or assist them in settling. KAUST scientists plan to decode the DNA shared by Ruegeria and create a detailed map showing which genes are “turned on” by the GTAs in the organisms receiving them.
“Corals and their associated microbes must be understood as a whole ‘metaorganism’; marine microbes are central to coral reef ecology in ways that the research community is just beginning to discover,” said Christian Voolstra, Assistant Professor of Marine Science at KAUST. “Advancing this frontier is important to us, and we are grateful to collaborate internationally with Mote and USF scientists who are breaking new ground in this important line of reef research.”
“What we’re learning in the lab could, in time, lead to a new understanding of coral reefs in the ocean,” said Dr. John Paul, Distinguished University Professor of Biological Oceanography at USF. “Reefs around the world host a number of bacteria that produce GTAs. By learning what these gene-swapping bacteria might contribute to coral life cycles, we can provide resource managers essential knowledge to protect or even enhance reefs.”