Monitoring microbiome of wildfire smoke, including bacteria and fungi, using PUF disk-type passive and High-volume active air samplers, using ambient air samples from Toronto, Ontario and the Alberta Oil Sands Region

Wildfire smoke occurs seasonally across North America, affecting air quality, atmospheric processes, and human health. Its impact on the airborne microbial community remains underexplored. We present the first integrated analysis of airborne bacteria and fungi, examining how wildfire smoke alters population structures in ambient air in the wildfire-prone Oil Sands Region (OSR) in Alberta, and in urban Toronto (influenced by long-range smoke transport). Airborne microorganisms (surveyed via 16S rRNA and ITS gene sequences) were collected during pre-wildfire and wildfire periods using High-Volume (Hi-Vol) and Passive (PUF-PAS) samplers. Microbial analysis and statistical analyses (PCoA, RDA, VPA) revealed a significant loss in microbial diversity and a homogenization of previously distinct regional community structures during wildfire exposure. Wildfire smoke enriches pollution- and stress-tolerant taxa, known for thermotolerance, oxidative stress resistance, and allergic or pathogenic potential. Diversity loss was correlated with elevated concentrations of PM2.5, CO, and O3, suggesting that both pollution and wildfire geography are ecological drivers of microbial shifts. Microbial and pollutant changes were confirmed to be fire-driven, not seasonal. Wildfire smoke is a biologically active agent that restructures the aerobiome. There is an urgent need to incorporate bioaerosol metrics into wildfire-health response frameworks in the context of accelerating climate change.