Diverse taxa of cyanobacteria produce β- 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, β- 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.

Toxin mixture in cyanobacterial blooms – a critical comparison of reality with current procedures employed in human health risk assessment

“…BMAA, originating from cyanobacterial cycad root symbionts of the genus Nostoc, was demonstrated to bioaccumulate at various trophic levels including in some of the traditional foods of these inhabitants of these islands (Cox et al 2003). However, recently Cox et al (2005) revealed that BMAA production by cyanobacteria appeared most likely to be a general phenomenon, as BMAA was detected in 95% of 21 cyanobacterial genera. Indeed, most recent GC-MS/MS analyses of Aph.…”

“…containing BGAS demonstrated large quantities of BMAA (Dietrich unpublished data). If BMAA is indeed involved in the aetiology of ALS/PDC, the findings of BMAA in BGAS may potentially explain the detection of BMAA in brain tissues of Canadians with Alzheimer's disease (Cox 2005). Although it would have to be established whether or not these patients had consumed BGAS at any given time.…”

“…However, the potential human toxin exposure via food that provides the basis for risk calculations is also largely determined by the degree of toxin contamination of a given food source as well as by the bioavailability of the toxin from the food type. Furthermore, although most likely an exception to the rule, bioaccumulation of cyanotoxins in the food chain, as is the case with β-N-methylamino-L-alanine (BMAA), may provide for an additional element of risk (Cox et al 2005).…”

“…Contrary to Spirulina, where direct production of toxin is yet uncorroborated, A. flos-aquae is known to be capable of producing the neurotoxic alkaloids anatoxin-a (Rapala et al 1993) and saxitoxins (Adelman et al 1982;Ferreira et al 2001;Mahmood and Carmichael 1986;Pereira et al 2000), as well as the neurotoxic, nonprotein amino acid BMAA (Cox et al 2005). Maatouk et al (2002) assumed that a mono-specific Aph.…”

“…However, the uptake of these toxins and their organ distribution appears to be mediated by specific transporters, of which most, if not all, remain unidentified in humans and other mammalian species (Fischer et al 2005). An exception to the latter is the uncommon, non-protein amino acid β-Nmethylamino-L-alanine (BMAA), a neurotoxin, which is probably produced by most likely all known groups of cyanobacteria (Cox et al 2005).…”