Bleached Coral

Warmer Temperature Makes Bacteria a Coral Killer, Study Says

Bleached Coral 

The white areas on this coral are a result of bleaching. Scientists are reporting progress toward understanding how this harmful process occurs.
Photo courtesy of the National Oceanographic and Atmospheric Administration.

Scientists are reporting the first identification of substances involved in the Jekyll-and-Hyde transformation that changes harmless marine bacteria into killers that cause "coral bleaching."

Their "NMR-Based Microbial Metabolomics and the Temperature-Dependent Coral Pathogen Vibrio coralliilyticus" study appears in the American Chemical Society' Environmental Science & Technology journal, Dan Bearden and colleagues note that bleaching already has destroyed up to 30 percent of the world's coral reefs, and scientists are searching for ways to slow or stop the damage. One known culprit is an ocean-dwelling bacterium, Vibrio coralliilyticus (V. coralliilyticus) that chokes-off corals' energy supply and kills these shell-clad marine animals. At lower temperatures, the bacteria are harmless to coral. But at warmer temperatures (above 75 degrees Fahrenheit) the bacteria become virulent and can kill coral.

The new study reports identification of three chemicals — betaine, glutamate, and succinate — that V. coralliilyticus produces in warmer water and are involved in the transformation. The discovery opens the door to understanding the biology involved in the complex interactions between corals and bacteria and unraveling the mystery of coral bleaching, the scientists indicated.

Bearden, Ph.D., works at the Hollings Marine Laboratory of the National Institute of Standards and Technology in Charleston, S.C.

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