Characteristics and Traceability Analysis of Microbial Assemblage in Fine Particulate Matter from a Pig House

SIMPLE SUMMARY: Fine Particulate Matter (PM(2.5)) can severely harm human and animal health because it can carry many harmful microorganisms and enter the deep respiratory tract. Due to the high breeding density and poor ventilation in large-scale pig farms, the concentration of PM(2.5) is higher indoors than outdoors. Therefore, it is very important to understand the composition of harmful microorganisms carried by PM(2.5) in pig houses and trace their sources and interactions with the environment. This study first monitored the environment of a piggery, identified the species and abundance of pathogenic bacteria and allergens on the collected PM(2.5) samples using high-throughput sequencing, then analyzed the interactions between microbial communities and between communities and environmental factors using network analysis, and finally, used the SourceTracker tool to predict the microbial traceability of PM(2.5). The results showed that the contribution of feces to producing airborne microorganisms was much higher than that of feed. ABSTRACT: Fine particulate matter (PM(2.5)) can carry numerous substances and penetrate deep into the respiratory tract due to its small particle size; associated harmful microorganisms are suspected to increase health risks for humans and animals. To find out the microbial compositions of PM(2.5) in piggeries, their interaction and traceability, we collected PM(2.5) samples from a piggery while continuously monitoring the environmental indicators. We also identified pathogenic bacteria and allergens in the samples using high-throughput sequencing technology. We analyzed the microbial differences of PM(2.5) samples at different heights and during different times of day and investigated the microbial dynamics among the PM(2.5) samples. To better understand the interaction between microorganisms and environmental factors among different microbial communities, we applied the network analysis method to identify the correlation among various variables. Finally, SourceTracker, a commonly used microbial traceability tool, was used to predict the source of airborne microorganisms in the pig house. We identified 14 potential pathogenic bacteria and 5 allergens from PM(2.5) in the pig houses, of which Acinetobacter was the dominant bacterium in all samples (relative abundance > 1%), which warrants attention. We found that bacteria and fungi directly affected the the microbial community. The bacterial community mainly played a positive role in the microbial community. Environmental variables mainly indirectly and positively affected microbial abundance. In the SourceTracker analysis using fecal matter and feed as sources and PM(2.5) sample as sink, we found that fecal matter made the greatest contribution to both bacterial and fungal components of PM(2.5). Our findings provide important insights into the potential risks of pathogens in PM(2.5) to human and animal health and their main sources.