Diatoms: A Novel Source for the Neurotoxin BMAA in Aquatic Environments

Abstract

Amyotrophic lateral sclerosis (ALS) or Lou Gehrig’s disease is a neurological disorder linked to environmental exposure to a non-protein amino acid, β-N-methylamino-L-alanine (BMAA). The only organisms reported to be BMAA-producing, are cyanobacteria – prokaryotic organisms. In this study, we demonstrate that diatoms – eukaryotic organisms – also produce BMAA. Ultra-high-performance liquid chromatography coupled with tandem mass spectrometry revealed the occurrence of BMAA in six investigated axenic diatom cultures. BMAA was also detected in planktonic field samples collected on the Swedish west coast that display an overrepresentation of diatoms relative to cyanobacteria. Given the ubiquity of diatoms in aquatic environments and their central role as primary producers and the main food items of zooplankton, the use of filter and suspension feeders as livestock fodder dramatically increases the risk of human exposure to BMAA-contaminated food.

The neurotoxin BMAA in aquatic systems : analysis, occurrence and effects

“…Commonly used derivatisation techniques in combination with LC-MS/MS analysis are AQC (e.g. [34,97,98]), propyl chloroformate (e.g. [91,99]) and dansyl chloride [100,101]), see Box 1.2 for explanation of AQC derivatised LC-MS/MS analysis.…”

“…The only study so far on BMAA production by cyanobacteria [99] does not provide evidence as the 5 experimental setup is flawed, there is too little evidence for correct BMAA identification and not all results are presented (Appendix A5.6). Diatoms might also be BMAA producers, as one study has shown that axenic diatom cultures contain BMAA [98]. Taken together, only two studies have identified cyanobacteria and diatoms as possible BMAA producers, but their findings have not yet been confirmed by other, independent laboratories.…”

“…For instance, some methods could not be reproduced because it was unclear how the elution programs was performed [96,98] and for another study, it was even impossible to tell which analytical procedure had been followed [146].…”

“…These concentrations are close to the detection limits of the previously mentioned LC-MS(/MS) studies in which no BMAA was detected, which range from 0. One LC-MS/MS based study has convincingly shown that axenic diatom cultures can contain BMAA at concentrations between 1.1 and 3.3 ng/g DW, the BMAA concentration in a cyanobacteria/diatom dominated field sample was 27.6 ng/g DW [98].…”

“…Recently, it was reported that also planktonic diatoms and dinoflagellates contain BMAA [98,142]. Therefore, in addition to on-going research on the role of BMAA in causing human neurodegenerative diseases, studies also focus on estimating concentrations of BMAA in aquatic ecosystems.…”