Neurotoxic amino acids and their isomers in desert environments

• Desert crust contains cyanobacterial toxins.
• Structural isomers of the neurotoxin BMAA are present in desert crust.
• The newly discovered cyanobacterial BMAA isomer AEG shows toxicity to Artemia salina.

Cyanobacteria are capable of producing a wide range of bioactive compounds including highly toxic molecules which affect a variety of molecular targets. These toxins are well known from aquatic environments, and their occurrence in terrestrial environments is now gaining attention. Of the toxins produced by cyanobacteria, β-N-methylamino-l-alanine (BMAA) is a neurotoxic amino acid linked to human neurodegenerative diseases including Amyotrophic Lateral Sclerosis (ALS), Alzheimer's and Parkinson's disease. Two isomers of BMAA are known to be produced by cyanobacteria in axenic culture and in cyanobacterial blooms. Desert crust material was assessed for the presence of BMAA isomers. In addition to BMAA, 2,4-diaminobutyric acid (DAB) and N-(2-aminoethyl)glycine (AEG), were found to be present in desert environments. Both BMAA and DAB are known to be toxic. A preliminary assessment of AEG toxicity was performed with Artemia salina. At high concentrations, AEG was shown to cause mortality of A. salina with paralysis observed at lower concentrations. These findings show that the co-occurrence of BMAA, DAB and AEG may lead to adverse human and animal health effects and future research should consider the interaction of these three isomers for their effect on human health in arid environments.