Blue-green algae linked to Alzheimer's disease

Apr 5 2005

An international team of researchers, including scientists from the University of Dundee have announced that cyanobacteria (blue-green algae) found throughout the world may produce a toxin linked to certain types of neurological disease.

Researchers have previously proposed a link between beta-methyl-amino-alanine (BMAA), a neurotoxic amino acid found in cyanobacteria and an Alzheimer’s-like neurodegenerative disease suffered by the Chamorro people on Guam in the Pacific. The Chamorro people eat the seeds from cycads, plants found only in warm regions of the world which were found to produce BMAA.

Dr. Paul Cox, Director of the Institute for Ethnomedicine of the National Tropical Botanical Garden in Hawaii, and his colleagues found that BMAA is produced by a cyanobacterium resident in special roots of the cycad. Interest increased when BMAA was found in brain tissues of several Alzheimer’s disease patients in Canada.

A network of cyanobacterial scientists, including Dr James Metcalf, Louise Morrison and Professor Geoffrey Codd of the School of Life Sciences at Dundee with Paul Cox, and partners in Stockholm and Hawaii are now investigating the widescale occurrence of BMAA throughout the cyanobacteria and its significance to health.

Professor Codd said, “Samples of cyanobacteria were collected from freshwaters, seas, soil, lichen, a cave and a hot spring from across the world. Of a sample of 30 cultures, ninety five percent of them were shown to produce BMAA”

The Dundee laboratory is internationally recognised for its research on various toxic substances in cyanobacterial blooms and how to reduce the problems which these can present to water-users and consumers. “Whilst our earlier surveys have shown toxin production to be common but patchy among cyanobacteria, for example in lakes, this is the first time that we have encountered such a widespread production of a toxin among the different cyanobacterial groups”, explains Codd.

The study raises questions, the scientists caution, “Whilst BMAA is neurotoxic, the nature of the association with human neurological disease remains uncertain” says Codd. “However we now know that BMAA is widely produced by cyanobacteria from throughout the world, in addition to a rather specialist cyanobacterium on a small Pacific island. This indicates that human exposure to BMAA may also occur more widely and that BMAA should be monitored in water resources, including reservoirs, if they contain cyanobacteria. Now that we know about BMAA in cyanobacteria, steps can be taken to reduce the risks to health which the substance may present.”

The findings of the international team are announced in the Proceedings of the National Academy of Sciences in the USA.