Cyanotoxin accumulation and growth patterns of biocrust communities under variable environmental conditions.

Biocrusts dominate the soil surface in deserts and are composed of diverse microbial communities that provide important ecosystem services. Cyanobacteria in biocrusts produce many secondary metabolites, including the neurotoxins BMAA, AEG, DAB, anatoxin-a(S) (guanitoxin), and the microcystin hepatotoxins, all known or suspected to cause disease or illness in humans and other animals. We examined cyanobacterial growth and prevalence of these toxins in biocrusts at millimeter-scales, under a desert-relevant illumination gradient. In contrast to previous work, we showed that hydration had an overall positive effect on growth and toxin accumulation, that nitrogen was not correlated with growth or toxin production, and that phosphorus enrichment negatively affected AEG and BMAA concentrations. Excess illumination positively correlated with AEG, and negatively correlated with all other toxins and growth. Basic pH negatively affected only the accumulation of BMAA. Anatoxin-a(S) (guanitoxin) was not correlated with any tested variables, while microcystins were not detected in any of the samples. Concerning toxin pools, AEG and BMAA were good predictors of the presence of one another. In a newly conceptualized scheme, we integrate aspects of biocrust growth and toxin pool accumulations with arid-relevant desertification drivers.

l-Serine Reduces Spinal Cord Pathology in a Vervet Model of Preclinical ALS/MND.

The early neuropathological features of amyotrophic lateral sclerosis/motor neuron disease (ALS/MND) are protein aggregates in motor neurons and microglial activation. Similar pathology characterizes Guamanian ALS/Parkinsonism dementia complex, which may be triggered by the cyanotoxin ß-N-methylamino-l-alanine (BMAA). We report here the occurrence of ALS/MND-type pathological changes in vervets (Chlorocebus sabaeus; n = 8) fed oral doses of a dry powder of BMAA HCl salt (210 mg/kg/day) for 140 days. Spinal cords and brains from toxin-exposed vervets were compared to controls fed rice flour (210 mg/kg/day) and to vervets coadministered equal amounts of BMAA and l-serine (210 mg/kg/day). Immunohistochemistry and quantitative image analysis were used to examine markers of ALS/MND and glial activation. UHPLC-MS/MS was used to confirm BMAA exposures in dosed vervets. Motor neuron degeneration was demonstrated in BMAA-dosed vervets by TDP-43+ proteinopathy in anterior horn cells, by reactive astrogliosis, by activated microglia, and by damage to myelinated axons in the lateral corticospinal tracts. Vervets dosed with BMAA + l-serine displayed reduced neuropathological changes. This study demonstrates that chronic dietary exposure to BMAA causes ALS/MND-type pathological changes in the vervet and coadministration of l-serine reduces the amount of reactive gliosis and the number of protein inclusions in motor neurons.

Analysis of Neurotoxic Amino Acids from Marine Waters, Microbial Mats, and Seafood Destined for Human Consumption in the Arabian Gulf.

Human health risks associated with exposure to algal and cyanobacterial toxins (phycotoxins) have been largely concerned with aquatic habitats. People inhabiting desert environments may be exposed to phycotoxins present in terrestrial environments, where cyanobacterial crusts dominate. Seafood comprises a significant portion of the human diet in desert environments proximal to an ocean or sea. Consequently, in addition to terrestrial exposure to cyanotoxins, the potential exists that seafood may be an important exposure route for cyanotoxins in desert regions. Understanding the possible risk of exposure from seafood will help create cyanotoxin health guidelines for people living in environments that rely on seafood. Commonly-consumed local seafood products destined for human consumption were purchased from a fish market in Doha, Qatar. Organs were excised, extracted, and analyzed for the neurotoxic amino acid ß-N-methylamino-L-alanine (BMAA) and the isomers 2,4-diaminobutyric acid (DAB) and N-2(aminoethyl)glycine (AEG). The presence and concentration of neurotoxic amino acids were investigated in organisms from various trophic levels to examine the potential for biomagnification. Although BMAA and isomers were detected in marine microbial mats, as well as in marine plankton net trawls associated with diatoms and dinoflagellates, in seafood, only AEG and DAB were present at low concentrations in various trophic levels. The findings of this study suggest that exposure to neurotoxic amino acids through seafood in the Arabian Gulf may be minor, yet the presence of BMAA in phytoplankton confirms the need for further monitoring of marine waters and seafood to protect human health.