Evolution of PM_2.5 bacterial community structure in Beijing's suburban atmosphere

Biosafety has become one of the greatest challenges facing humanity. Outbreaks of infectious diseases caused by bacteria and viruses have had a huge impact on public health. In addition, non-severe polluted air quality has gradually become the norm; however, literature on the impacts of bioaerosols under long-term exposure to low concentrations of PM_2.5 in China is limited. This study analyzed the evolution of the PM_2.5 bacterial community in the Huairou district of Beijing under different pollution conditions. We used high-throughput sequencing to seasonally analyze samples over a year (from July 2018 to May 2019) and winter samples from different years (2015, 2016, 2018, and 2019). The results showed that the bacterial diversity and community composition of PM_2.5 were significantly different in different seasons, whereas under different pollution levels, there were no significant differences. During the observation period, the number of bacterial species decreased with the increase in pollution; however, a high proportion of bacteria can exist as core species under different pollution levels for a long time. Furthermore, bacteria can be relatively stable in the local environment during the same season but in different years. Although the relative abundances of different bacteria change differently with the variation in pollution level, there is no statistical difference. Importantly, there was a higher abundance of opportunistic pathogenic bacteria when the air quality index was 0-100 in winter. This study comprehensively revealed the characteristics of the evolution of bacterial communities under different pollution levels and in different years and emphasized the health effects of non-pollution air quality. This study can provide a theoretical basis for establishing a sound environmental microbial monitoring and defense system.