β-N-methylamino-l-alanine (BMAA) and isomers: Distribution in different food web compartments of Thau lagoon, French Mediterranean Sea

Abstract

The neurotoxin BMAA (β-N-methylamino-l-alanine) and its isomer DAB (2,4-diaminobutyric acid) have been detected in seafood worldwide, including in Thau lagoon (French Mediterranean Sea). A cluster of amyotrophic lateral sclerosis (ALS), a neurodegenerative disease associated with BMAA, has also been observed in this region. Mussels, periphyton (i.e. biofilms attached to mussels) and plankton were sampled between July 2013 and October 2014, and analyzed using HILIC-MS/MS. BMAA, DAB and AEG (N-(2-aminoethyl)glycine) were found in almost all the samples of the lagoon. BMAA and DAB were present at 0.58 and 0.83, 2.6 and 3.3, 4.0 and 7.2 μg g(-1) dry weight in plankton collected with nets, periphyton and mussels, respectively. Synechococcus sp., Ostreococcus tauri, Alexandrium catenella and eight species of diatoms were cultured and screened for BMAA and analogs. While Synechococcus sp., O. tauri and A. catenella did not produce BMAA under our culture conditions, four diatoms species contained both BMAA and DAB. Hence, diatoms may be a source of BMAA for mussels. Unlike other toxins produced by microalgae, BMAA and DAB were detected in significant amounts in tissues other than digestive glands in mussels.

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

“…These findings are quite in agreement with other studies that did not detect BMAA in cyanobacterial samples by underivatised LC-MS/MS analysis (e.g. [76,77,79,103,198]) and also with the detection of BMAA in diatoms by underivatised LC-MS/MS analysis (e.g. [198]).…”

“…Although a limited number of studies have determined this fraction so far, soluble bound BMAA seems to occur in a diversity of organisms: cycad seeds (this study and [92]), periphyton [198], plankton [98,198], and bivalves [89,103,198]. It is therefore recommended to include soluble bound BMAA in future studies, for instance by hydrolysing the total sample (e.g.…”

“…It is therefore recommended to include soluble bound BMAA in future studies, for instance by hydrolysing the total sample (e.g. [93,100,197]), or by releasing it from the dried extract [89,98,103,198]. When only free and precipitated bound BMAA are determined, the soluble bound fraction can be overlooked, potentially resulting in a substantial underestimation of the total sample's BMAA content.…”

“…The recent attention for soluble bound BMAA in cycad seeds (Chapter 7 and [92]), periphyton [198], plankton [98,198], and bivalves [89,103,198] calls for revision of the relatively common extraction strategy of determining free BMAA in the aqueous extract and precipitated bound ("protein associated") BMAA in the hydrolysed pellet (e.g. Chapter 2 and [33,35,187,189,190,204]).…”

“…In vitro, BMAA can be incorporated into proteins and can be associated to proteins through non-covalent bonding [65,90], but in vivo experiments with bacteria do not show protein incorporation [91]. Only few studies look at soluble bound BMAA in an isolated fraction (e.g., [89,92,103,198]). In studies where total BMAA (i.e., hydrolysis of the total sample) is (also) determined, ignoring soluble bound BMAA does not lead to an underestimation of the total BMAA concentration.…”