Abstract
Ancient mariners knew that dust whipped up from deserts by strong winds travelled long distances, including over oceans. Satellite remote sensing revealed major dust sources across the Sahara. Indeed, the Bodélé Depression in the Republic of Chad has been called the dustiest place on earth. We analysed desert sand from various locations in Chad and dust that had blown to the Cape Verde Islands. High throughput sequencing techniques combined with classical microbiological methods showed that the samples contained a large variety of microbes well adapted to the harsh desert conditions. The most abundant bacterial groupings in four different phyla included: (a) Firmicutes—Bacillaceae, (b) Actinobacteria—Geodermatophilaceae, Nocardiodaceae and Solirubrobacteraceae, (c) Proteobacteria—Oxalobacteraceae, Rhizobiales and Sphingomonadaceae, and (d) Bacteroidetes—Cytophagaceae. Ascomycota was the overwhelmingly dominant fungal group followed by Basidiomycota and traces of Chytridiomycota, Microsporidia and Glomeromycota. Two freshwater algae (Trebouxiophyceae) were isolated. Most predominant taxa are widely distributed land inhabitants that are common in soil and on the surfaces of plants. Examples include Bradyrhizobium spp. that nodulate and fix nitrogen in Acacia species, the predominant trees of the Sahara as well as Herbaspirillum (Oxalobacteraceae), a group of chemoorganotrophic free-living soil inhabitants that fix nitrogen in association with Gramineae roots. Few pathogenic strains were found, suggesting that African dust is not a large threat to public health.
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Acknowledgements
We would especially like to thank Dr Agathe Stricker of the International Committee of the Red Cross in Geneva, Switzerland for organising the collection of the ‘Sandman’ samples from the Republic of Chad. On board the Stad Amsterdam, Ilja Willems and Kapitein Richard Slootweg were particularly helpful. We thank Dora Gerber, Michal Parkan, Xavier Perret, Wolfgang Streit and Luiz Roesch for their unstinting help. Dyson Ltd, Tetbury Hill Malmesbury Wiltshire SN16 0RP, UK generously donated a hand-held vacuum cleaner. We relied heavily on Wikipedia (in three languages) and Genoscope to accurately place bacteria and their metabolisms. In Switzerland, the work was supported by the Fonds National Suisse de la Recherche Scientifique (Projects 3100AO-104097 and 3100A0-116858), the Département de l’Instruction Publique du Canton de Genève and the Université de Genève. Work in the United States of America was made possible by grants from the National Science Foundation (Grant Number MCB-0454030) and the United States Department of Agriculture (Grant Numbers 2005-35319-16300, 00067345).
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Favet, J., Lapanje, A., Giongo, A. et al. Microbial hitchhikers on intercontinental dust: catching a lift in Chad. ISME J 7, 850–867 (2013). https://doi.org/10.1038/ismej.2012.152
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DOI: https://doi.org/10.1038/ismej.2012.152
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