MIT researchers achieve breakthrough on red tide toxin
It's one of the mysteries of nature: How do microscopic plants in the ocean generate so much poison that they form red tide, massive floating algae blooms that kill the fish in their path and make entire shellfish beds toxic to people? Researchers don't even know why the little creatures secrete these chemicals, let alone how to make the poisons efficiently in their labs.
Now, chemists at the Massachusetts Institute of Technology may have discovered the recipe for a major type of red tide - though not the type commonly found in New England. The research opens the door to a better understanding of an affliction that costs costal communities tens of millions of dollars in lost catches, human illness, and wildlife injuries, such as the manatees who died in a red tide outbreak near Florida last spring.
By combining a chemical similar to an enzyme in the ocean with chemicals found in the algae, researchers set off a chain reaction that created abundant amounts of a toxin called brevetoxin that is common in Florida.
"A lot of people thought that this type of cascade may be impossible," said Timothy Jamison, an MIT assistant professor who, working with graduate student Ivan Vilotijevic, proved a 22-year-old theory about red tide known as "the Nakanishi cascade hypothesis." He added, "The trick is to give it a little push in the right direction."
Red tide researchers praised the MIT results, the cover story in today's edition of the journal Science, saying the ability to create red tide toxins in the lab may help them better understand the conditions that foster outbreaks, which could lead them to an antidote to the poisons. The technique may also have an important side benefit: A toxin similar to brevetoxin has shown potential as a treatment for cystic fibrosis.
"It's a really creative piece of work. I think it's quite inspired," said Jeffrey Wright, a professor of marine science at the University of North Carolina Wilmington, who has done pioneering work in identifying the toxins in red tide.
"The more we understand the way these molecules are put together by these red tide organisms, the more we are able to understand the whole phenomenon," said Don Anderson, a leading authority on red tide at Woods Hole Oceanographic Institution.
The single-cell algae that cause red tide, called dinoflagellates, produce an array of remarkably complex toxins, including the saxitoxins that are commonly produced by red tide outbreaks in New England waters. Earlier this month, a Maine fisherman and his family had to be rushed to the hospital after contracting paralytic shellfish poisoning from eating mussels contaminated with saxitoxin that he had scraped off a barrel floating offshore. Saxitoxin is chemically very different from brevetoxin.
Anderson said researchers have made great progress in predicting red tide outbreaks and tracking their movement along the coast, but pinning down the cause of the mass poisoning has been harder. Some theorize that the dinoflagellates produce toxic chemicals as a defense mechanism in response to changes in the current or water temperature, but Anderson said it may be an evolutionary fluke that the dinoflagellates' waste product is poisonous to people and other creatures.
Shellfish contaminated with red tide are not harmed by the toxins.
The poisons, until now, have been very difficult to work with, requiring years of laboratory time to create only a few milligrams of brevetoxin or other compounds. Koji Nakanishi of Columbia University argued 22 years ago that the plants make their poisons in a cascade of steps that is somehow spurred by the water itself, but, until the MIT research, other labs could not prove Nakanishi was right.
Jamison said the extra molecules they added to trigger the creation of toxins by the dinoflagellates may mimic an enzyme found in ocean water.
Wright, the North Carolina professor, said the MIT research still needs to be replicated by other researchers, but if Jamison has discovered nature's way of making brevetoxin, his findings should apply to numerous other similar toxins that are found in red tides around the world.
"This is an elegant piece of work," said John Schwab of the National Institute of General Medical Sciences, which helped fund the research.
Scott Allen can be reached at allen@globe.com.
