Airborne Bacterial Communities of PM2.5in Beijing-Tianjin-Hebei Megalopolis, China as Revealed by Illumina MiSeq Sequencing: A Case Study

Bacteria are ubiquitous and abundant in the atmosphere and some of them are potential pathogens known to cause diseases or allergies in humans. However, the quantities and compositions of total airborne bacterial community and their relationships with environmental factors remain poorly investigated. Here, a case study of the total airborne bacteria of PM2.5collected at six cities in Beijing-Tianjin-Hebei (BTH) megalopolis, China were profiled using quantitative polymerase chain reaction (qPCR) and Illumina MiSeq (PE300) sequencing. qPCR results showed the high abundance of total airborne bacteria of PM2.5in BTH, ranging from 4.82 × 104± 1.58 × 103to 2.64 × 105± 9.63 × 104cell m−3air, and averaged 1.19 × 105cell m−3air. The six PM2.5samples were classified into three groups. Proteobacteria, Cyanobacteria, Actinobacteriaand Firmicuteswere the four dominant phyla of PM2.5. 18 common potential pathogens with extremely low percentage (3.61%) were observed, which were dominated by Enterococcus faeciumand Escherichia coli. Plants and soil are probably the main sources of bacteria in PM2.5, as suggested by the high percentages of Chloroplast, plant-associated bacteria (e.g., Rhizobialesand Sphingomonadales) and soil-inhabiting bacteria (e.g., Burkholderialesand Pseudomonadales). Variation partitioning analysis (VPA) indicated that the atmospheric pollutants explained the most of the variation (31.90%) in community structure of PM2.5, followed by meteorological conditions (15.73%) and the chemical compositions of PM2.5(11.32%). The case study furthers our understanding of the diversity and composition of airborne bacterial communities of PM2.5in BTH, and also identified the main factors shaping the bacterial communities.