Phylogenetic analysis of bacterial species compositions in sand dunes and dust aerosol in an Asian dust source area, the Taklimakan Desert

Airborne microorganisms (bioaerosol) from the China desert region, which are released into the atmosphere, disperse by the Asian dust event and affect ecosystems, human life, and atmospheric processes in downwind areas. However, the dynamics of airborne bacteria over the China desert regions have rarely been investigated. In this study, we analyzed bacterial communities in aerosols of the Asian dust source region (Taklimakan Desert) and compared them with the bacterial communities in sand dunes, for evaluating the mixtures from sand area to atmosphere. Air samples were collected at 10 m above the ground level from Dunhuang City during a dust event. The cell densities of airborne bacteria during a dust event were ten times more than that in non-dust periods. The 16S rDNA clone libraries from four air samples mainly belonged to two phyla, Firmicutes and Proteobacteria. During a dust event, the proportion of Proteobacteria clones decreased, whereas that of Firmicutes clones increased. Sand samples were collected from the sand dunes in four sampling sites of the Taklimakan Desert. The bacterial communities in sand samples comprised of the members of Firmicutes and Actinobacteria. The clones of Firmicutes in both air and sand samples included Bacillus species, constituting more than 10 % of total clones. Airborne bacterial communities would be carried by the dust events from sand dunes. Propionibacterium species from the class Actinobacteria that were dominant in sand samples were not detected in the air samples, suggesting that atmospheric stressors eliminate some bacterial species. Presumably, airborne bacterial communities in the Asian dust source region are composed of local environmental bacteria, and their dynamics depend on the occurrence of a dust event.