BALTIMORE, MD — From a 60-year-old Karlodinium Veneficum (K. veneficum) culture kept at the U.K.’s Plymouth Laboratory, a research team led by the University of Maryland Center for Environmental Science (UMCES) discovered the cause of the Chesapeake Bay’s fish-kill, which was originally blamed on another phytoplankton, Pfiesteria piscicida. UMCES researchers determined that Pfiesteria was not, in fact, the cause of the Bay’s fish-kill; rather, the karlotoxins found in K. veneficum were to blame.
In a paper recently published in Nature Scientific Reports, using surface plasma resonance and a suite of bioassays, the authors report the specific functions of membrane pores formed by these karlotoxins. Moreover, the formation is a highly targeted mechanism involving the cell membrane and sterol-specificity; cholesterol, in this case.
"What is so unique about this toxin is its mode of action, how it works," said Allen Place, an UMCES Professor and expert in biochemistry, serving as the primary investigator on the project. "To consume other phytoplankton, it generates holes in their cell walls, creating a porous membrane through which other ions can flow; this incapacitates and eventually kills its prey, which it then eats."
This analysis proves karlotoxins generate pores in membranes with desmethyl sterols – like cholesterol, phytosterols and ergosterol – that weaken membranes, disrupt motor function, cause cells to swell, and eventually, burst, all for the sake of capturing and devouring susceptible organisms. They use the toxin as a defense mechanism, too.
"Think of a venomous snake that stores venom inside special glands – the venom can’t harm the snake, in other words, it can’t self-intoxicate due to the make-up of its anatomy, but it can certainly harm creatures it comes into contact with," Place said. "The same holds true for K. veneficum, and it’s not unique to Chesapeake Bay; this has a world-wide distribution. And it’s sensitive to environmental inputs such as global warming, so the higher the temperature, the more abundant this organism becomes."
Although the toxin has proven deadly to fish, shellfish, small sharks and even laboratory mice, it’s important to note that the presence of cholesterol deactivates the threat, similar to how vinegar neutralizes lye. There is little physical impact to people. The impact to the environment, however, could potentially be significant.
UNIVERSITY OF MARYLAND CENTER FOR ENVIRONMENTAL SCIENCE
The University of Maryland Center for Environmental Science leads the way toward better management of Maryland’s natural resources and the protection and restoration of the Chesapeake Bay. From a network of laboratories located across the state, UMCES scientists provide sound evidence and advice to help state and national leaders manage the environment, and prepare future scientists to meet current global challenges.
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Katie Ross, Communications Coordinator
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