Scripps Oceanography Research pegs ID of red tide killer

“It’s possible that bacteria of this type play an important role in terminating algal blooms and regulating algal bloom dynamics in temperate marine waters all over the world,” said Mayali.

The research study, which was coauthored by Scripps Professors Peter Franks and Farooq Azam, is published in the May 1 edition of the journal Applied and Environmental Microbiology.

“Our understanding of harmful algal blooms and red tides has been fairly primitive. For the most part we don’t know how they start, for example,” said Franks, a professor of biological oceanography in the Integrative Oceanography Division at Scripps. “From a practical point of view, if these RCA bacteria really do kill dinoflagellates and potentially other harmful algae that form dense blooms, down the road there may be a possibility of using them to mitigate their harmful effects.”

The researchers based their results on experiments conducted with samples of a red tide collected off the Scripps Pier in 2005. Because RCA bacteria will not grow under traditional laboratory methods, Mayali developed his own techniques for identifying and tracking RCA through highly delicate “micromanipulation” processes involving washing and testing individual cells of Lingulodinium. He used molecular fluorescent tags to follow the bacteria’s numbers, eventually matching its DNA signature and sealing its identity.

Cells of the dinoflagellate Lingulodinium polyedrum, collected at sea during a bloom in the summer of 2005, shows reddish areas signifying natural chlorophyll fluorescence, blue areas revealing DNA and green... Click here for more information.

“The work in the laboratory showed that the bacterium has to attach directly to the dinoflagellate to kill it,” said Mayali, “and we found similar dynamics in the natural bloom.”

Franks said he found it a bizarre concept of scale that Lingulodinium dinoflagellates, which at 25 to 30 microns in diameter are known to swim through the ocean with long flagella, or appendages, are attacked by bacteria that are about one micron in size and can’t swim.

“It’s somewhat shocking to think of something like three chipmunks attaching themselves to an elephant and taking it down,” said Franks.