Aerosol and Air Quality Research, 20: 2834–2845, 2020 ISSN: 1680-8584 print / 2071-1409 online Publisher: Taiwan Association for Aerosol Research https://doi.org/10.4209/aaqr.2020.01.0030 Characterization of Airborne Microbial Aerosols during a Long-range Transported Dust Event in Eastern China: Bacterial Community, Influencing Factors, and Potential Health Effects Ying Rao1,2,3#, Heyang Li2,4#, Mingxia Chen5, Qingyan Fu6, Guoshun Zhuang1*, Kan Huang1,7,8* 1 Center for Atmospheric Chemistry Study, Shanghai Key Laboratory of Atmospheric Particle Pollution and Prevention (LAP3), Department of Environmental Science and Engineering, Fudan University, Shanghai 200433, China 2 Third Institute of Oceanography, Ministry of Natural Resources, Xiamen 361005, China 3 Health Center of Minnan Normal University, Zhangzhou 363000, China 4 Fujian Provincial Key Laboratory of Marine Ecological Conservation and Restoration, Xiamen 361005, China 5 Department of Biological technology and Engineering, HuaQiao University, Xiamen 361021, China 6 Shanghai Environmental Monitoring Center, Shanghai, 200030, China 7 Institute of Eco-Chongming (IEC), Shanghai 202162, China 8 Institute of Atmospheric Sciences, Fudan University, Shanghai 200433, China ABSTRACT 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 2– – + 2+ communities to be wind speed and the SO2, SO4 , NO3 , PM10, NH4 , and Ca concentrations. Keywords: Airborne bacteria; Bacterial community structure; Influencing factors; Long-range transported dust. INTRODUCTION Shulls, 1978). More than 25% of the particles over the earth’s surface was composed of bioaerosols (Jones and Atmospheric aerosols which contained biological substances Harrison, 2004). Bioaerosols in PM2.5 were estimated in the such as microorganisms or biomolecules were called range of 3–11% by weight (Womiloju et al., 2003; Boreson bioaerosols. Of which, the part that contained microorganisms et al., 2004). The emission intensity of the global microbial was called microbial aerosols. Atmospheric microbial aerosols aerosols varied from 10–1000 Tg y–1, while the portion of are closely related to air pollution, biosphere, cloud chemistry, bacterial aerosols was about 0.74–28.1 Tg y–1 (Després et climate, and human health (Delort et al., 2010; Peccia et al., al., 2012). The concentration of bacterial aerosols near the 2010; Fröhlich-Nowoisky et al., 2016). Bioaerosols was unique surface of land was usually higher than 1 × 104 cells m–3 as circulation of the materials, ecological balance and so many (Bauer et al., 2002), while the concentration of bacteria biological phenomena were all relevant to it (Mancinelli and above the ocean was much less of about 100–1000 cells m–3 (Prospero et al., 2005; Griffin et al., 2006). The diurnal variation of the concentrations of bacteria in the boundary layer was significantly influenced by # These authors contributed equally to this work. meteorological factors, e.g., wind speed (Sun et al., 2003). One study conducted in Xiamen, China, suggested the * Corresponding author. concentrations of bacterial aerosols were associated with the E-mail address: [email protected] (G. Zhuang); weather conditions, showing the lowest during sunny days [email protected] (K. Huang) while the highest during the haze period (Liao, 2013). Copyright The Author(s). This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are cited. Rao et al., Aerosol and Air Quality Research, 20: 2834–2845, 2020 2835 Similar to the transport of particulate matters, the revealed. Factors influencing the bacterial community and transport of microbial aerosols in the atmosphere was potential threat on human health were discussed. It should passive (Sun et al., 2003). The residence time of bacteria in be noted that the assessment of the magnitude of dust impact the atmosphere was about one week (Burrows et al., 2009). on human health was beyond the scope of this study. Dust storm is one of the important natural phenomena in the earth system (Goudie and Middleton, 2006; Ravi et al., METHODOLOGY 2011; Shao et al., 2011). Some studies found that bacterial aerosols from deserts or arid areas could be transported Aerosol Sampling intercontinentally (Polymenakou et al., 2008; Lim et al., 2011; Microbial Aerosol Sampling Hara and Zhang, 2012; Barberán et al., 2014) and the bacterial Microbial aerosol samples were collected on the roof of community of the downwind areas were significantly the 4th Teaching Building of Fudan University in Shanghai, changed (Maki et al., 2013). During the long-range transport, China (121°29′E, 31°14′N; 20 m above ground level). No the aeolian dust mixed with reactive gases and polluted strong point sources were located around this site. This site aerosols, and it was common that bacteria adhered on the has been regarded as a representative of the urban environment particles (Yamaguchi et al., 2012). The abundances of of Shanghai, standing for the mixing of traffic, residential, bacterial aerosols collected at 1000 km downstream far from and industrial sources. Microbial aerosol samples were the dust source area during the dust episode were 1–10 times obtained on the 37-mm sterile filter membrane (FMCE) by more than that during the non-dust period (Jeon et al., 2011). using the sampler (XMX-CV; Dycor, Canada) at a flow rate Significant differences of the bacterial community were found of 530 L min–1. All the samples obtained were kept under between dust samples and non-dust samples. Aquabacterium –20°C until DNA extraction. The sampling information is sp., Flavobacteriales, and Prevotellaceae were dominant in shown in Table 1. dust samples while Propionibacterium sp., Bacillus sp., and Acinetobacter sp. were dominant in non-dust samples (Lee Airborne Aerosol Sampling et al., 2009). It was found that dust plumes posed threat on Atmospheric PM2.5 samples were synchronously collected human health not only in the dust source areas but also the with the microbial aerosols at the same site. Aerosol samples downwind areas (Griffin, 2007; Yamaguchi et al., 2012; were collected on Whatman Grade 41 filters (Whatman Inc., Goudie, 2014). The diffusion of bioaerosols in atmosphere Maidstone, UK) by a medium-volume sampler (flow rate: –1 may harm human health, including infectious diseases, 77.59 L min ; TSP/PM10/PM2.5-2; Beijing Geological allergy, and occupational hazard (Douwes et al., 2000; Den Instrument-Dickel Co., Ltd., China). All the samples were Boer et al., 2002). Some bacteria carried by dust were put in polyethylene plastic bags immediately after sampling pathogenic such as Neisseria meningitidis and Clostridium and then reserved in a refrigerator. The filters were weighed perfringens. Meningococcal meningitis caused by Neisseria before and after sampling using an analytical balance (reading meningitidis was epidemic throughout sub-Saharan Africa precision: 10 µg; 2004 MP; Sartorius) after stabilizing in as Neisseria meningitidis can adhere on dust particles and constant temperature (20 ± 1°C) and humidity (40 ± 2%) for activate by high iron contents in dust (Thomson et al., 2009). 48 hours. All the procedures were strictly quality controlled Clostridium perfringens has been found as the primary to avoid any possible contamination of the samples. pathogen of food poisoning (Grass et al., 2013) and has also Meteorological parameters were measured by an automated been observed in dust which may cause disease by inhalation weather station (Vaisala). (Leski et al., 2011). In this study, one dust event in Shanghai during February DNA Extraction and PCR Amplification 20–21, 2016, was monitored based on the air mass backward The frozen filter membrane was cut into pieces and put trajectory modeling and the chemical tracer of aerosols. The into a Lysing Matrix E tube, and then the total environmental 16S rRNA gene analysis method was applied to investigate genomic DNA was extracted using a FastDNA® Spin Kit for the structure of bacterial community in atmospheric aerosols Soil (MP Biomedical, USA) according to the standard protocol. before, during, and after the dust. The differences of the The purity and concentration of the DNA was examined by bacterial community structure during different periods were NanoDrop® ND-2000 UV-Vis Spectrophotometer (NanoDrop Table 1. Sampling information during February 18–22, 2016, in Shanghai. –3 * Group