Stony coral tissue loss disease is a fatal disease for great star corals. Characterized by the development of white lesions that lead to loss of polyps (tiny soft-bodied organisms similar to sea anemones). Eventually, the white lesions move across the coral, killing coral tissue. Subsequently, nothing but the white coral skeleton is left behind. Now, scientists have found a way to beat this coral disease with the help of probiotics— helpful bacteria that attack and displace harmful pathogens. They can also possibly incite immune responses against them.
Researchers at the Smithsonian Marine Station in Fort Pierce, Fla., successfully stopped further advancement of the disease’s symptoms. However, the reason behind the propagation of this fatal disease is yet to be known. Researchers think that the disease is bacterial, and antibiotics have been helpful in treating the infections. However, there lies the risk of developing antibiotic resistance in yet-to-be-identified pathogens, and the risk of reinfection is also high. These two factors drove the Smithsonian group into trying out probiotic treatment in late 2020 in 30 infected great star coral colonies.
The beneficial microbes were identified in corals that showed resistance to the deadly disease. “We noticed that one of the coral fragments would not get infected … so one of the first things we did was try to culture the microbes that are on this coral,” says microbiologist Blake Ushijima, who developed the probiotic used in the team’s experiment. “These microbes produce antibacterial compounds … and one had a high level of activity against bacteria from diseased corals,” which act as a probiotic and neutralize pathogens.
The identified bacterium has been named McH1-7, and forms the main ingredient in the probiotic paste that divers delivered to the infected corals. To deliver the medicine, the divers covered the infected coral colonies using plastic bags and injected the paste into the bags using a syringe. In other cases, the divers coated the lesions with the paste directly and smoothened out the paste with a gloved hand, apparently covering the infected regions.
The team monitored the corals’ health for two and a half years. The disease was stopped from spreading further, or was slowed down in all eight colonies treated with the probiotic paste inside bags. The paste put directly on the coral did not show any improvement. On average, the disease’s advance was halted to only 7 percent of tissue, compared to 30 percent in untreated colonies.
However, amidst the encouraging results, coauthor Valerie Paul cautions against declaring probiotics a cure. She doubts using heavily weighted plastics to cover the corals during probiotic treatment.
In conclusion, the idea of coral probiotics has been thrown around for decades, but this is the first time it has been tested in wild settings. According to Ushijima, this might open new doors in treating corals. ting diseases in corals.
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