The dynamics and assembly patterns of airborne pathogen communities in the municipal food waste treatment system and its risk implications

While municipal solid waste (MSW) provides an ideal habitat for pathogen propagation, the dynamics and assembly of airborne pathogen communities in these environments remain largely unknown. Here, we combined amplicon and metagenomics with spatiotemporal sampling to study inhalable particulate matter-carried potential pathogenic bacteria at full-scale food waste treatment plants (FWTPs), alongside comparisons to urban air in the area. The results showed that pathogenic bacteria constituted a notable portion (64.5 % ± 20.6 %, n = 75) of the total bacterial communities in FWTPs-impacted air, with species and relative abundance 2–4 times higher than that of urban air, and contributed over 50 % of pathogens to the outdoor air. Airborne pathogen community structures were highly shaped by sampling sites (i.e. treatment units), but conserved across seasons (summer vs. winter) and particle sizes (PM_2.5 vs. PM₁₀). Notably, Acinetobacter johnsonii-dominated pathogens (i.e. biofilm-related species) presented high levels of aerosolization and consistently occupied the upper-representative niches in all neutral models, highlighting their persistent exposure risk. Furthermore, pathogen community assembly was strongly driven by stochastic processes (58.8 %–96.8 %), while environmental variables explained only limited variations (3.4 %–28.7 %). In particular, the relative importance of stochastic processes clearly increased along an outdoor-to-indoor gradient (84.9 %–96.5 % vs. 71.3 %–76 %), which might be related to indoor anthropogenic activities that weaken microbial network stability and environmental filtering effects. This work enhances our knowledge of the dynamic behaviors and risk of airborne pathogen communities in MSW disposal and underscores the role of FWTPs in disseminating airborne pathogens.