Long-range transport of airborne microorganisms by Asian dust events: Bioaerosols relating to human health

The bioaerosols relating to human health are possibly transported by the westerly wind traveling at high altitudes over East Asia. However, the long-range transport of bioaerosols has not been demonstrated by analyzing the microbial communities in aerosols such as desert mineral particles and anthropogenic pollutants transported by the westerly wind. Here, airborne microbial compositions were investigated in high-altitude aerosols collected during the Asian dust events in Japan island. This was further compared to the ground-level aerosols collected sequentially at more than seven sampling sites distributed from Asian dust source region to downwind areas in East Asia (Asian desert; Tsogt-Ovoo, Asian continental cities; Erenhot, Beijing, Yongin, Japanese island cities; Yonago, Suzu, Noto Peninsula). The cell concentrations and taxonomic diversities of airborne bacteria decreased from the Asian continental area to the Japan island area. Terrestrial bacterial populations belonging to Firmicutes and Actinobacteria showed higher relative abundance at downwind areas during Asian-dust events. Additionally, some pathogenic microorganisms such as NTM-PD bacteria (Mycobacterium species) increased in relative abundance in correspondence to the increase of black carbon concentrations. In contrast, the food fermenting bacteria, such as Natto bacteria (Bacillus subtilis), were detected and isolated from the high-altitude aerosols and actually made Natto. Presumably, Asian dusts carry potential pathogen and fermenting microorganisms, thereby impacting upon the human societies.