The Microbiome of Size-Fractionated Airborne Particles from the Sahara Region

Abstract

Diverse airborne microbes affect human health and biodiversity, and the Sahara region of West Africa is a globally important source region for atmospheric dust. We collected sizefractionated (>10, 10−2.5, 2.5−1.0, 1.0−0.5, and <0.5 μm) atmospheric particles in Mali, West Africa and conducted the first cultivation-independent study of airborne microbes in this region using 16S rRNA gene sequencing. Abundant and diverse microbes were detected in all particle size fractions at levels higher than those previously hypothesized for desert regions. Average daily abundance was 1.94 × 10 5 16S rRNA copies/m 3 . Daily patterns in abundance for particles <0.5 μm differed significantly from other size fractions likely because they form mainly in the atmosphere and have limited surface resuspension. Particles >10 μm contained the greatest fraction of daily abundance (51−62%) and had significantly greater diversity than smaller particles. Greater bacterial abundance of particles >2.5 μm that are bigger than the average bacterium suggests that most airborne bacteria are present as aggregates or attached to particles rather than as free-floating cells. Particles >10 μm have very short atmospheric lifetimes and thus tend to have more localized origins. We confirmed the presence of several potential pathogens using polymerase chain reaction that are candidates for viability and strain testing in future studies. These species were detected on all particle sizes tested, including particles <2.5 μm that are expected to undergo long-range transport. Overall, our results suggest that the composition and sources of airborne microbes can be better discriminated by collecting size-fractionated samples.

Respirable Metals, Bacteria, and Fungi during a Saharan–Sahelian Dust Event in Houston, Texas

“…Dominant genera recovered in our analyses include those that have previously been linked to African dust, are pathogenic, or both. These include Rubellimicrobium, noted during African dust events in the Eastern Mediterranean and coastal Europe; , Bacillus, an animal and plant pathogen ubiquitous in deserts and Saharan dust; , Escherichia, a human pathogen identified in an African dust intrusion in southern Spain and in Mali; Staphylococcus, a component of the desert soil/dust microbiome and a leading nosocomial antibiotic-resistant pathogen; Sphingomonas, reported in desert dust from North Africa and in the Middle East ,, and common in the aerobacteriome; , Kaistobacter, a soil-inhabiting species but rarely reported in urban and dust-related bioaerosols; Deinococcus and Pontibacter, previously identified in Saharan dust/soil; ,, Streptomyces, a plant pathogen found in desert soil/dust and decaying biomass; and Rothia, an opportunistic soil pathogen.…”

Size-Resolved Community Structure of Bacteria and Fungi Transported by Dust in the Middle East

“…Previous studies have associated the source of the air-mass with the aerobiome’s community composition (e.g., Bowers et al, 2011 ; Peter et al, 2014 ; Grantham et al, 2015 ; Gat et al, 2017 ; Rahav et al, 2019 ; Tignat-Perrier et al, 2019 ; Lang-Yona et al, 2020 ). Fewer studies have compared the aerobiome’s community composition in terms of particles of different size (e.g., Polymenakou et al, 2008 ; Yamamoto et al, 2012 ; Helin et al, 2017 ; Stern et al, 2021 ). Examining both variables using a single dataset provides a novel opportunity to assess how the microbial community composition of each particle size-class is affected by, or displays, the variance caused by different air-mass sources.…”

Infectious Diseases Associated with Desert Dust Outbreaks: A Systematic Review

“…All studies were published between 2004 and 2021 [ 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 , 57 , 58 , 59 , 60 ]. The affected regions that were studied were Asia (32/51, 62.7%), followed by Europe (9/51, 17.6%), America (6/51, 11.8%), Africa (4/51, 7.8%) and Australia (1/51, 2.0%).…”

“…and Coxiela burnetti , as well as Coccidioides spp. fungus and influenza A virus [ 10 , 16 , 22 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 ]. The remaining studies reported opportunistic pathogens, mostly Bacillus spp., Aspergillus spp., etc.…”

“…As far as means of transmission and distance are concerned, potential human pathogens were found in all size fractions of dust tested, including the smaller particles that are more likely to undergo long-distance transport and reach the distal airways via inhalation [ 16 ]. In addition, some of the isolated pathogens, such as Coxiella burnetti , are well-known for their ability to be transmitted via inhalation from long distances.…”