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Tuesday, April 5, 2005



Water-scum toxin
linked to nerve ailments

A small aquatic and photosynthetic bacteria found throughout the world might produce a toxin linked to certain neurological diseases such as a paralytic disease among Guam's Chamorros, researchers have discovered.

Cyanobacteria, more commonly called pond scum, is known to produce molecules hazardous to human health, but the researchers' findings are the first indicating they also generate a toxin associated with some types of neurological disease.

"The ubiquity of cyanobacteria in terrestrial as well as freshwater, brackish and marine environments suggests a potential for widespread human exposure," the scientists said in a study published today in the Proceedings of the National Academy of Sciences.

The researchers included Paul Cox, director of the Institute for Ethnomedicine at the National Botanical Garden on Kauai; Robert Bidigare, director, University of Hawaii Center for Marine Microbial Ecology and Diversity; and Georgia Tien, curator of the UH center's cyanobacteria collection.

In earlier studies, Cox connected high incidence of amyotrophic lateral sclerosis, or Lou Gehrig's disease, among Chamorros to eating fruit bats or flying foxes, which fed on cycad plants with cyanobacteria in the roots.

The toxin, a nonprotein amino acid called BMAA, was known to occur only in cycads until 2003, the scientists said.

However, it was discovered recently in the brain tissues of nine Canadian Alzheimer's patients, triggering questions about other forms of cyanobacteria as the source since Canada does not have cycad plants.

In the new study, researchers examined 30 cyanobacteria samples from worldwide environments maintained at UH, Stockholm University in Sweden and the University of Dundee, Scotland. They found that 95 percent of the cyanobacterial groups produce BMAA toxin, which they said "is of both ecological and evolutionary significance."

Bidigare said Cox theorized in his earlier study that toxic amino acids could be concentrated in proteins, passed up the food chain and slowly released over time as proteins are metabolized, producing "slow toxin."

Cox said the link between BMAA and neurological disease still has not been proved, but the new study indicates human exposure might not be limited to the Guam ecosystem and Chamorros.

Further investigations are needed because of possible health consequences of chronic exposure to low doses of BMAA accumulated in proteins, the scientists said.

They also suggest monitoring toxic amino acid concentrations in drinking water contaminated by cyanobacteria blooms and in invertebrates, fish or grazing animals used for human consumption.

"Given the global importance of marine cyanobacterial blooms, such as those generated by iron-laden dust in the Atlantic and Pacific oceans, a broader analysis of the production and fate of BMAA in marine ecosystems is also needed," they reported.

Cyanobacteria is often called blue-green algae. This name does not reflect any relationship between the cyanobacteria and other organisms called algae, according to the University of California-Berkeley Web site. Cyanobacteria are related to the chloroplast that makes food in algae.

Bidigare's center has the world's largest cyanobacterial collection, with more than 2,000 strains of blue-green algae assembled about 20 years ago by Dr. Greg Patterson, formerly of UH.

Algal strains isolated in Hawaiian waters were found to contain neurotoxic amino acid, but potential effects are not known, Bidigare said. "It's not clear whether the toxin is present in fish."

Bidigare's group has received $800,000 from the National Marine Fisheries Service to survey miroalgae around the Hawaiian Islands and screen fish and marine mammal tissue for toxin.

Algal blooms can extend for miles in the ocean and sometimes are so extensive they are mistaken for a black oil slick on the surface of the water, Bidigare said.

"It's the higher concentrations of cyanobacteria that produce toxin. ... We don't know if it's passed up through the food chain and if it's a risk."

UH scientists also want to test a theory that toxins might be responsible for beaching of marine mammals, often blamed on Navy underwater acoustics tests, Bidigare said.

The researchers will work with the state veterinarian to get tissue samples of marine animals that die of known and unknown causes to see if there is a correlation between cyanobacteria and beachings, he said.

Extensive cyanobacteria blooms around the islands have measurable toxin that can leak into the sea water, Bidigare said.

"With a very large bloom of cyanobacteria, if it is leaking out amino acid and the water had a very high concentration, it's possible a mammal swimming through this might pick it up. We plan to see if there are any links."

Proceedings of the National Academy of Sciences
www.pnas.org/


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