Modification of atmospheric sand-associated bacterial communities during Asian sandstorms in China and South Korea

Abstract

The transport of desert soil into the atmosphere during desert sandstorms can affect the Earth's climate and environmental health. Asian desert sandstorms occur almost every year during the Spring, as the atmosphere in the Northern hemisphere warms. It is conceivable that these Asian desert sandstorms may transport microbes from deserts, such as the Gobi and Taklamaken deserts, over long distances in China, east Asia and the Pacific. In this study, we examined local atmospheric sand particle-associated bacterial populations collected in the absence (sterile sand exposed for 24 h to the air in the absence of a sandstorm) and presence of sandstorms in five Asian cities. We used pyrosequencing of PCR-amplified 16S rDNA genes from sand-extracted total DNA to overcome cultivation limitations of bacterial enumeration. We found that 490% of the control and sandstorm sequences could be classified as representing bacteria belonging to four phyla: Proteobacteria, Bacteriodetes, Actinobacteria and Firmicutes. The sand-associated bacterial populations in sandstorm samples were distinct from sandassociated bacteria in the absence of a sandstorm. Members of the phylum Proteobacteria were found to significantly increase in sandstorm samples (P = 0.01). Principal component analyses showed that the sand-associated bacterial populations were best clustered by sampling year, rather than location. DNA sequences representing bacteria belonging to several genera (including putative human pathogens) were observed to increase in sand-associated samples from sandstorms, whereas others were found to decrease, when comparing sand-associated bacterial populations versus those in control samples, suggesting human/ environmental implications of sandstorm events.

Impacts of Saharan Dust Intrusions on Bacterial Communities of the Low Troposphere

“…Although similar studies of airborne bacterial diversity across different altitudes during a dust intrusion are currently nonexistent, our results are comparable to the diversity patterns observed in other studies dealing with desert dust events. Thus, samples collected during the dust intrusion showed a higher diversity (Chao1 and Shannon H index, Supplementary Table S2) than non-dust related samples, which is in agreement with other previous studies 4,13,30,34,35,60 . Additionally, rarefaction analysis (Suplementary Fig.…”

“…The Saharan origin of these microbial communities is revealed by the high conformity of principal bacterial genera described for Saharan desert with those present in these samples 63 . Thus, the most abundant bacterial species in all samples taken during the dust event (∼30-40% of the total sequences in these samples) (Suplementary Table S3), gruped in three different phyla, previously reported during desert dust events 35,60,[63][64][65] : (a) Proteobacteria-Rhizobiales (Rhizobium and Microvirga), Sphingomonadales, Rhodobacterales (Rubellimicrobium), (b) Actinobacteria-Geodermatophilaceae; (c) Firmicutes-Bacillaceae,. Most of these species are well known for being extremely stress-resistant, including, high temperatures, such as Rubellimicrobium 63 , high radiation and desiccation, specially Geodermatophilus 64,65 , or spore formation such as Bacillus, which increase the probability of survival during transportation 66 .…”

“…6). This result suggest that, changes in the local atmospheric microbial composition near the surface caused by the dust intrusions may remain for several days after the major event has passed 60 . This desert influence in the atmosphere could extend even to several weeks in the presence of thermal inversion phenomena, which are frequently associated with hot air desert intrusions in the Iberian Peninsula during the winter 62 .…”

Bacterial Communities in Marine Aerosols Revealed by 454 Pyrosequencing of the 16S rRNA Gene*

“…However, based on traditional incubation methods and microscopy analysis, both the diversity and abundance of marine aerosol bacteria were thought to be relatively low (Pósfai et al 2003;Hultin et al 2011). Bacillus sp., which are typical soil bacteria, were reported to be the major aerosol bacteria in marine aerosol over Asia and could easily be transported to Korea, Japan, and even farther to North America (Hua et al 2007;Maki et al 2010;Smith et al 2013;An et al 2014). This indicates that the bacterial community in marine aerosols is more diverse than previously thought.…”

Next-generation sequencing propels environmental genomics to the front line of research

“…An et al (2014) highlight the changes caused by bacterial communities transported along with the dust in atmospheric sandstorms, over planetary distances. The authors hypothesize that the origin of the sandstorms may be explained by variations among sites with regards to wind sources and trajectories.…”