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Toxic Free Radical Produced by Pfiesteria piscicida: A New Paradigm in Marine Toxins


First discovered in the late 1980s, Pfiesteria bloomed in 1997 in Chesapeake Bay tributaries in association with fish kills and human health problems, resulting in large economic losses due to lost seafood sales and tourism. That outbreak led to a large research effort to understand the causes and prevent or minimize the impacts of many harmful algal blooms (HABs), especially of the dinoflagellate Pfiesteria, through the Ecology and Oceanography of Harmful Algal Blooms (ECOHAB) program. Many HABs produce toxins that cause animal and human sickness and mortality. The question of whether Pfiesteria species produce a toxin has been hotly debated ever since. The researcher will present his recent findings, funded in part by ECOHAB, that Pfiesteria produces a toxin that has a novel structure and mechanism of toxicity and is also easily degraded under natural conditions, both of which may explain why identifying and characterizing the toxin has been so difficult.

Seminar Abstract

Metal-containing organic toxins produced by Pfiesteria piscicida are responsible for highly toxic free radical production. These unstable compounds were characterized for the first time by corroborating data generated from a number of analytical chemistry techniques including Electron Paramagnetic Resonance Spectroscopy, Nuclear Magnetic Resonance Spectroscopy, and mass spectrometry. The toxicity of the metal-containing toxins is due to metal-mediated free radical production. The ephemeral nature of these radical species explains the observed on/off nature of toxicity associated with Pfiesteria, as well as previously reported difficulty in observing the molecular target. This discovery represents the first formal isolation and characterization of a radical forming toxic organic-ligated metal complex isolated from estuarine/marine dinoflagellates. Reported findings underscore the active role of metals interacting with biological systems in the estuarine environment and set the stage for further evaluation of the role of this toxin in the environment. These findings have just been published in Environmental Science & Technology (2007; 41(4); 1166-1172).

Seminar Details

March 19, 12:00 – 1:00PM
SSMC-3, Room #4527*
1315 East-West Hwy
Silver Spring, MD 20910

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