Diverse taxa of cyanobacteria produce beta-N-methylamino-L-alanine, a neurotoxic amino acid

Abstract

Cyanobacteria can generate molecules hazardous to human health, but production of the known cyanotoxins is taxonomically sporadic. For example, members of a few genera produce hepatotoxic microcystins, whereas production of hepatotoxic nodularins appears to be limited to a single genus. Production of known neurotoxins has also been considered phylogenetically unpredictable. We report here that a single neurotoxin, beta-N-methylamino-L-alanine, may be produced by all known groups of cyanobacteria, including cyanobacterial symbionts and free-living cyanobacteria. The ubiquity of cyanobacteria in terrestrial, as well as freshwater, brackish, and marine environments, suggests a potential for wide-spread human exposure.

Fig. 1.

Cyanobacterial strains that produce BMAA representing different morphological sections. (a) The bloom-forming, filamentous, and colony-forming Trichodesmium thiebautii (section III). (Scale bar: 100 μm.) (b) The unicellular Synechococcus PCC 6301 (section I). (Scale bar: 1 μm.) (c) The filamentous Symploca PCC 8002 (section III). (Scale bar: 10 μm.) (d) The filamentous, nonbranching, and heterocystous (H) Nostoc PCC 7107 (section IV). (Scale bar: 10 μm.) (e) The filamentous, heterocystous (H) and branching (arrow) Fischerella PCC 7521 (section V). (Scale bar: 15 μm.)

Fig. 2.

HPLC chromatograph of BMAA peak in Chroococcidiopsis indica GT-3–26 (section II) (solid line) and BMAA authenticated standard (dashed line) obtained by using fluorescence detection.

Fig. 3.

Satellite photograph of a Trichodesmium bloom by using SeaWiFS imagery for spectral imaging at 443, 490, and 550 nm off the eastern coast of Florida on October 30, 1998.