New Discoveries of the Relationship Between Corals & Bacteria

Seems like the relationship between corals and bacteria are becoming a hot subject in the scientific world and a lot of publications on this are coming out every week. This week, we came across a recent paper describing the dynamic biological relationship between corals and marine bacteria in the journal Nature.

Coral reefs as we know them may never be the same again if we disrupt the very complex environmental balance.

The Aquarickettsia bacterium is the first member of a newly identified genus, and was discovered during a study of the Caribbean staghorn coral microbiome by Oregon State University (OSU) molecular biologist Rebecca Vega Thurber and her colleagues.

Using sophisticated computer programs and search algorithms to query the databases and map genetic associations, the researchers discovered that the newly named bacterium, Candidatus Aquarickettsia rohweri—as well as other closely related members of the newfound genus, Candidatus Aquarickettsia—are commonly found in the microbiomes of sponges, corals, and other aquatic organisms worldwide.

Reefs are a sensitive equilibrium of living creatures that all depend on each other.

“The primary thing we want people to take away is that this bacterium is a parasite. We know that it causes the coral to not be able to grow, but only under specific conditions,” Vega Thurber says.

At low levels, Ca. A. rohweri seems to be harmless, but when it proliferates in a nutrient-rich environment—such as fertilizer-polluted water—corals suffer. The parasite steals energy from corals. Analysis shows that the bacterium carries a gene, Tlc1, which allows it to rob coral cells of adenosine triphosphate (ATP), their basic energy source.

Vega Thurber thinks the parasites kill corals in one of two ways: “They directly sap the coral of its nutrition and resources; or alternatively, make it susceptible to additional pathogens.” Whether the bacterium kills the coral on its own or compromises its immunity to other diseases, it’s clear that Ca. A. rohweri, when found in abundance, is a deadly threat.

Once the balance is shifted, certain species disappear from the reef, and the only hardest like these soft corals are left alive.

This new finding and the techniques used, open a new door toward understanding the complex relationship between, microbes and corals, and the very thin line between mutualistic symbiosis and parasitism. Hopefully it will help understand what is killing corals along the Florida coast.

This is a scientific evidence that a slight shift of parameters can bring dramatic consequences, as we often experience it in our reef tanks.

Vincent Chalias

Vincent is a coral passionate aquarist with extensive experience in the industry, travelling the world to learn about corals. His background is a master degree in Marine Aquaculture. He set up the first Indonesian Coral mariculture farms at the beginning of the century and spent over 20 years in Indonesia running them. He's been extensively diving and documenting corals all over the Indo-Pacific.