Abstract
Atmospheric transport is a major vector for the long-range transport of microbial communities, maintaining connectivity among them and delivering functionally important microbes, such as pathogens. Though the taxonomic diversity of aeolian microorganisms is well characterized, the genomic functional traits underpinning their survival during atmospheric transport are poorly characterized. Here we use functional metagenomics of dust samples collected on the Global Dust Belt to initiate a Gene Catalogue of Aeolian Microbiome (GCAM) and explore microbial genetic traits enabling a successful aeolian lifestyle in Aeolian microbial communities. The GCAM reported here, derived from ten aeolian microbial metagenomes, includes a total of 2,370,956 non-redundant coding DNA sequences, corresponding to a yield of ~31 × 106 predicted genes per Tera base-pair of DNA sequenced for the aeolian samples sequenced. Two-thirds of the cataloged genes were assigned to bacteria, followed by eukaryotes (5.4%), archaea (1.1%), and viruses (0.69%). Genes encoding proteins involved in repairing UV-induced DNA damage and aerosolization of cells were ubiquitous across samples, and appear as fundamental requirements for the aeolian lifestyle, while genes coding for other important functions supporting the aeolian lifestyle (chemotaxis, aerotaxis, germination, thermal resistance, sporulation, and biofilm formation) varied among the communities sampled.
Highlights
Desert dust is one of the main sources of aerosols[1], including both mineral particles and aeolian microorganisms, supplying the atmosphere with a heavy load of microbes that can be transported across large distances[2]
We provide here the first attempt at describing the Red Sea Aeolian microbiome from a functional metagenomics perspective, and reviewed the literature on the functions postulated to be important in supporting successful Aeolian microbial transport to propose a set of targeted genes that help define the Aeolian lifestyle
Samples collected from air masses transported by winds from the prevailing NW direction were characterized by higher dust ranging from 119 to 156 μg m−3 and bacterial loads ranging from 109 × 103 to 212 × 103 cells m−3 compared to the single sample collected from an air mass transported by winds originating from the SE (5 μg m−3 and 288.89 103 cells m−3) (Fig. 1b), which is characteristic of these air masses[33]
Summary
Desert dust is one of the main sources of aerosols[1], including both mineral particles and aeolian microorganisms, supplying the atmosphere with a heavy load of microbes that can be transported across large distances[2]. A set of functions was selected to be analyzed in the airborne metagenomes, these functions are aerosolization[13], allowing microbes to be entrained from surfaces (soils, plants or water) to the air facilitated by gas vesicles inside the cells, aerotaxis[14] and chemotaxis[15], which are the movement of microbes under the influence of oxygen or chemical gradient that allow them to be positioned at the surface of their habitat, UV radiation[16] and heat resistance[17], which function in repairing the DNA damages induced by UV radiation and thermal stresses, germination[18] and sporulation[19], where the cells can form spores, which allow them to survive desiccation and exposure to UV radiation and germinate under harsh conditions, and biofilm formation[20] that enable the microorganisms to attach to surfaces such as dust particles We propose here this set of functions as a parsimonious set of traits that delineates capacities that, in combination, allow biological particles to survive atmospheric transport. Metagenomic databases (e.g. EBI Metagenomics)[32] lack information on aeolian microbes, despite their interest to unveil the functional strategies underpinning survival under harsh conditions, capabilities for attachment and survive long-distance transport on dust particles, and impacts on organisms, including humans
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