As an important part of atmospheric aerosol, airborne bacteria have major impacts on human health. However, variations of airborne community structure due to human-induced activities and their possible impact on human health have not been well understood. In this study, we sampled atmospheric microbial aerosols in three Chinese cities (Shanghai, Xiamen, and Zhangzhou) with contrasting social-economic levels and analyzed the bacterial composition using high-throughput sequencing methods. A high similarity of the predominant phyla was observed in three cities but the relative abundances were quite different. At the genus level, the most dominant genus in Shanghai and Xiamen was Deinococcus while the most dominant genus in Zhangzhou was Clostridium. The different characteristics of airborne bacterial in the three cities above may be ascribed to the environmental variables affected by human over-activities such as the vehicle exhausts and coal-burning emissions in Shanghai, the tourist aggregation and construction works in Xiamen, the extensive uses of chemical fertilizers, and agricultural activities in Zhangzhou. The variation of the bacterial community and the pathogenic bacteria detected in three cities would have a potential threat to human health.

Samples of atmospheric microbial aerosols were collected before, during, and after a dust invasion in Shanghai and analyzed using 16S rRNA high-throughput sequencing. The bacterial community structures in the mixed pollutive aerosols and dust were characterized, and the key environmental factors were identified. The dominant phyla were Proteobacteria, Actinomycetes, and Firmicutes, and the relative abundance of Acidobacteria increased significantly during the episode. Additionally, marked differences in the relative abundances of the 22 detected genera were observed between the three sampling stages: The dominant genera were Rubellimicrobium and Paracoccus prior to the arrival of the dust but became Deinococcus and Chroococcidiopsis during the invasion and then Clostridium and Deinococcus afterward. Notably, the relative abundance of Cyanobacteria, which is known to cause hepatotoxicity and promote tumor growth in humans, grew substantially during the event. Finally, statistical analysis revealed the largest environmental factors affecting the bacterial communities to be wind speed and the SO2, SO4 2-, NO3 -, PM10, NH4 + , and Ca 2+ concentrations.