Sheng publishes in PNAS
Prof. Jian Sheng working with microscopes
Destructive alga is vicious predator rather than helpless prey, university researchers say
MINNEAPOLIS / ST. PAUL ( 01/11/10 ) – A team of researchers, led by University of Minnesota aerospace engineering and mechanics faculty member Jian Sheng, has discovered new information about a toxic alga that shows it is a vicious, venom-producing predator rather than helpless prey. The alga has been blamed for harmful algal blooms known as “brown tide” that have resulted in massive fish kills in Chesapeake Bay and other waterways.
The researchers studied K. veneficum, a toxic alga found in salt water. Each year millions of dollars are spent on measures to control these organisms around the globe. The species is known to release a substance called karlotoxin, which is extremely damaging to marine wildlife.
This role of producing karlotoxin by the organisms was previously understood to be a form of self-defense against fish and other natural predators to relieve grazing pressure. However, in a series of experiments using 3-D digital holographic microscopy initially developed at The Johns Hopkins University, Sheng and his colleagues from around the country have found that the release of these karlotoxins now also serve the purpose of stunning prey before ingestion. This shifts the perception of the organism previously seen as prey to that of predator.
The research paper entitled “A dinoflagellate exploits toxins to immobilize prey prior to ingestion” was published today in the current issue of the prestigious scientific journal Proceedings of the National Academy of Sciences (PNAS). Researchers in addition to Sheng who are part of the team include Joseph Katz, a professor of mechanical engineering in the Whiting School of Engineering at The Johns Hopkins University; Edwin Malkiel, an adjunct associate research scientist in Johns Hopkins’ Department of Mechanical Engineering; Jason E. Adolf, an assistant professor in the University of Hawaii’s Department of Marine Science; and Allen R. Place, a professor in the University of Maryland Biotechnology Institute’s Center of Marine Biotechnology.
“In the paper, we have answered why these complicated molecules are made in nature in the first place and identify a possible alternative mechanism causing massive bloom,” said Sheng, a University of Minnesota fluid mechanics expert who began this research while earning his doctorate in Katz's lab at Johns Hopkins. “We further suggest a new venue of predicting and eventually mediating the bloom events.”
Using 3-D high-speed holographic microscopy, the researchers studied the relationship between K. veneficum and its prey, the rice-shaped, single-celled algae called cryptophytes. They found that the released karlotoxins by K. veneficum depolarize the prey cell’s membrane and cause the prey to slow down until they are ultimately ingested by the alga, assumedly so as to increase predation success rate and promote its own growth. This significantly shifts the understanding about the alga. Instead of mortality prevention, the organism’s actions relate more closely to growth promotion.
The University of Minnesota Department of Aerospace Engineering and Mechanics is one of 12 academic departments and 18 research centers that make up the Institute of Technology, the University's college of science and engineering.