Production of β-methylamino-L-alanine (BMAA) and Its Isomers by Freshwater Diatoms.

Jake P Violi,Anne Colville,Simon M Mitrovic,Jordan A Facey,Kenneth J Rodgers

doi:10.3390/toxins11090512

Jake P Violi, Anne Colville + Show 3 more

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https://doi.org/10.3390/toxins11090512

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Journal: Toxins	Publication Date: Sep 2, 2019
Citations: 37	License type: CC BY 4.0

Affiliation: University of Technology Sydney

Abstract

β-methylamino-L-alanine (BMAA) is a non-protein amino acid that has been implicated as a risk factor for motor neurone disease (MND). BMAA is produced by a wide range of cyanobacteria globally and by a small number of marine diatoms. BMAA is commonly found with two of its constitutional isomers: 2,4-diaminobutyric acid (2,4-DAB), and N-(2-aminoethyl)glycine (AEG). The isomer 2,4-DAB, like BMAA, has neurotoxic properties. While many studies have shown BMAA production by cyanobacteria, few studies have looked at other algal groups. Several studies have shown BMAA production by marine diatoms; however, there are no studies examining freshwater diatoms. This study aimed to determine if some freshwater diatoms produced BMAA, and which diatom taxa are capable of BMAA, 2,4-DAB and AEG production. Five axenic diatom cultures were established from river and lake sites across eastern Australia. Cultures were harvested during the stationary growth phase and intracellular amino acids were extracted. Using liquid chromatography triple quadrupole mass spectrometry (LC-MS/MS), diatom extracts were analysed for the presence of both free and protein-associated BMAA, 2,4-DAB and AEG. Of the five diatom cultures analysed, four were found to have detectable BMAA and AEG, while 2,4-DAB was found in all cultures. These results show that BMAA production by diatoms is not confined to marine genera and that the prevalence of these non-protein amino acids in Australian freshwater environments cannot be solely attributed to cyanobacteria.

Highlights

These results show that been published on the production of β-methylamino-L-alanine (BMAA) production by diatoms is not confined to marine genera and that the prevalence of these non-protein amino acids in Australian freshwater environments cannot be solely attributed to cyanobacteria
domoic acid (DA) was thought to be the only toxin produced by diatoms, three reports have been published on the production of β-methylamino-L-alanine (BMAA) and its isomer 2,4-diaminobutyric acid (2,4-DAB) by marine diatoms [4,5,6]
Fragilaria did not have detectible levels of BMAA, and Cyclotella did not have detectable levels of AEG. 2,4-DAB was detected in all the cultures (Table 3)

Summary

Introduction

Many algal groups, including cyanobacteria, dinoflagellates and diatoms, are capable of forming dense blooms under favourable conditions. Algal blooms are of great epidemiological and ecological significance since they produce a diverse range of chemicals which can cause toxic effects to humans and livestock, including skin irritation (dermatoxins), hepatic damage (hepatotoxins), and neuronal damage (neurotoxins) [1,2]. The production of toxins by diatoms was first reported in the 1980s, when the marine and estuarine diatom genus Pseudo-nitzschia was found to produce the neurotoxic amino. DA was thought to be the only toxin produced by diatoms, three reports have been published on the production of β-methylamino-L-alanine (BMAA) and its isomer 2,4-diaminobutyric acid (2,4-DAB) by marine diatoms [4,5,6].

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