By Avigayil Kadesh
Could a viral remedy that works for humans also protect corals against a deadly disease in the complex marine ecosystem?
Award-winning Tel Aviv University (TAU) molecular biologist Eugene Rosenberg, working in collaboration with Ilil Atad of his own laboratory and TAU coral expert Yossi Loya, believes so. He has developed a treatment for corals infected by bacteria that cause deadly “white plague” disease, which affects an estimated nine percent of Favia favus corals on the Eilat coral reef in the Red Sea.
Based on a successful strategy in human medicine, the Israeli method uses a virus called BA3 to inject lethal genetic material into the white plague bacteria. Laboratory experiments showed that BA3 was effective against these microbes, and subsequent field experiments in the Gulf of Eilat demonstrated that it works in real life too.
The researchers injected the virus into a group of diseased coral that was surrounded by a circle of healthy corals. An identical control group did not receive the virus.
After 24 hours, the difference in the outcome was significant, Rosenberg reported at the American Society for Microbiology's general meeting in June. In the test group, the infection was stopped in its tracks and the disease did not spread to the neighboring corals. In the untreated control group, the white plague disease progressed rapidly and spread to seven of the 10 healthy neighbors.
The next step is to develop an effective way to spread lab-synthesized therapeutic viruses over large areas of an infected coral reef, said Rosenberg, winner of the 2002 Procter & Gamble Award for Applied and Environmental Microbiology for his pioneering use of bacteria to clean up spilled oil on tankers, pipelines and beaches.
Caring about corals
One of the most surprising discoveries during the course of their research, said Rosenberg, was that some corals are already resistant to infection by the white plague pathogen. When the researchers tested the three corals in the control group that remained uninfected, they discovered that the BA3 virus was already present in their biological composition.
"We found that this is a natural process that goes on all the time. What we are doing is only shifting the situation in favor of the virus," he explained.
The TAU study is of interest not only to Israelis concerned about corals living in the Red Sea, but also to scientists in more than 100 countries where corals are essential to fostering biodiversity and protecting coastlines.
Loya and fellow coral experts are concerned that corals are increasingly endangered by pathogenic bacteria as well as pollution and harmful fishing practices.
Treating bacterial infections in corals is not easy because corals don’t produce antibodies and therefore cannot be immunized. Antibiotics are not a viable option because releasing these drugs into the sea harms the marine environment.
That’s why the Israeli antidote to specific pathogenic coral bacteria is a crucial breakthrough. Because corals in different regions of the world are infected with different pathogens, microbiologists will now be able to develop specific therapeutic viruses for each location, based on the methods used by Rosenberg and his colleagues.