A variety of types of blue-green algae all produce the same molecule, a potential neurotoxin, a new report suggests. The results, published online this week by the Proceedings of the National Academy of Sciences, represent the first time that unrelated species of cyanobacteria have been found to produce the same potentially hazardous substance.

Cyanobacteria can produce a wide range of molecules that are harmful to humans, but which species generate which compounds has so far been quite unpredictable. Paul Alan Cox of the National Tropical Botanical Garden in Hawaii and his colleagues studied five different morphological sections of cyanobacteria, as well as cyanobacterial symbionts taken from lichen and other plant species. They discovered that 95 percent of all genera of cyanobacteria produce a molecule identified as BMAA, a suspected neurotoxin that has been recently detected in the brains of some Alzheimer's sufferers. The amount of BMAA manufactured by the algal samples varied widely. The scientists thus posit that BMAA production and storage is a function of either growth conditions or life cycle stages of the bacteria.

Because of the widespread nature of cyanobacteria, the researchers suggest that it might be wise to monitor levels of BMAA in drinking water sources that contain cyanobacterial blooms. They note: "The ubiquity of cyanobacteria in terrestrial, as well as freshwater, brackish and marine environments, suggests a potential for widespread human exposure."