Aspassia D. Chatziefthimiou

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 β-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.

Microbial Characterization of Qatari Barchan Sand Dunes

This study represents the first characterization of sand microbiota in migrating barchan sand dunes. Bacterial communities were studied through direct counts and cultivation, as well as 16S rRNA gene and metagenomic sequence analysis to gain an understanding of microbial abundance, diversity, and potential metabolic capabilities. Direct on-grain cell counts gave an average of 5.3 ± 0.4 x 105 cells g-1 of sand. Cultured isolates (N = 64) selected for 16S rRNA gene sequencing belonged to the phyla Actinobacteria (58%), Firmicutes (27%) and Proteobacteria (15%). Deep-sequencing of 16S rRNA gene amplicons from 18 dunes demonstrated a high relative abundance of Proteobacteria, particularly enteric bacteria, and a dune-specific-pattern of bacterial community composition that correlated with dune size. Shotgun metagenome sequences of two representative dunes were analyzed and found to have similar relative bacterial abundance, though the relative abundances of eukaryotic, viral and enterobacterial sequences were greater in sand from the dune closer to a camel-pen. Functional analysis revealed patterns similar to those observed in desert soils; however, the increased relative abundance of genes encoding sporulation and dormancy are consistent with the dune microbiome being well-adapted to the exceptionally hyper-arid Qatari desert.