Microbiome of Saharan dust aerosols

In this study, Saharan dust aerosols (n=19) were sampled from East Mediterranean (Crete, Greece) using a high-volume TSPs sampler (TISCH). Dust atmospheric particles were collected on precombusted (450 °C for 5 h) 20 × 25 cm quartz filters (Pall, 2500QAT-UP). The sampling resolution was 48 h, at a flow rate of 85 m3 h−1. We established a reliable analytical protocol for extracting DNA from these Saharan dust particles. Together with biological quantification and identification, chemical analysis was performed, including metals, major ions, phospholipids and sugars.

Results show that the number of Eucaryotic DNA copies were 30 times higher than the bacterial copies during the dust events. The bacterial community composition in the collected dust aerosol as the most abundant Phyla were Proteobacteria (37%) followed by Actinobacteria (22%) and Firmicutes (13%). Furthermore, we analyzed five (n=5) intense dust events using magic angle spinning solid-state 31P-NMR. The results show that the typical functional groups in P speciation, were orthophosphate and monophosphate esters which sharing the same chemical shift (H3PO4 and RH2-PO4), phosphate diesters (R1R2 HPO4) and pyrophosphate (H4P2O7). No phosphonates were detected (C-P bond) in dust samples. Monophosphate esters and diesters are mainly found in nucleotides and their derivatives (e.g., DNA, RNA, AMP, ADP and ATP) but also in phospholipids, and as such, they constitute the majority of atmospheric organic-P. These organic-P compounds have C-O-P bonds and are easily hydrolyzed in the marine environment by alkaline phosphatase enzyme, providing an important source of P in the aquatic ecosystems when Saharan dust is deposited.