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 >90% 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 sand-associated 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.

Figure 1

The location of the sampling site cities in China and South Korea, and the two major Asian deserts (Gobi and Taklamaken). The edges of the deserts are indicated by dashed yellow lines.

Figure 2

The relative composition of phyla of the sandstorm and control sand-associated bacterial populations. The samples on the left represent the sand-associated controls from non-sandstorm days, while those on the right represent sand-associated bacteria from sandstorm samples. See the Materials and methods for the naming scheme of the samples.

Figure 3

A UPGMA clustering tree of the sandstorm and control sand-associated bacterial populations using a Bray–Curtis similarity index (97% cutoff) among samples, as described in the Materials and methods. Each sample was normalized to 3400 sequences.

Figure 4

Normed PCA using phyla composition data (a) or OTU composition (b) data generated by R. Red letters are used to represent samples from 2011, whereas green letters are used to represent samples from 2010. See the Materials and methods for the naming scheme of the samples.