Metagenomic profiling of ARGs in airborne particulate matters during a severe smog event

Highlights: • Tetracycline, β-lactam and aminoglycoside resistance genes had high abundance in airborne PMs. • Airborne PMs contained higher level of ARGs in smog days than in non-smog days. • Composition of ARGs in airborne PMs was comparatively more similar to those of soils. • Airborne bacteria and ARGs showed complicated co-occurrence patterns. Information is currently limited regarding the distribution of antibiotic resistance genes (ARGs) in smog and their correlations with airborne bacteria. This study characterized the diversity and abundance of ARGs in the particulate matters (PMs) of severe smog based on publicly available metagenomic data, and revealed the occurrence of 205 airborne ARG subtypes, including 31 dominant ones encoding resistance to 11 antibiotic types. Among the detectable ARGs, tetracycline, β-lactam and aminoglycoside resistance genes had the highest abundance, and smog and soil had similar composition characteristics of ARGs. During the smog event, the total abundance of airborne ARGs ranged from 4.90 to 38.07 ppm in PM_2.5 samples, and from 7.61 to 38.49 ppm in PM₁₀ samples, which were 1.6–7.7 times and 2.1–5.1 times of those in the non-smog day, respectively. The airborne ARGs showed complicated co-occurrence patterns, which were heavily influenced by the interaction of bacterial community, and physicochemical and meteorological factors. Lactobacillus and sulfonamide resistance gene sul1 were determined as keystones in the co-occurrence network of microbial taxa and airborne ARGs. The results may help to understand the distribution patterns of ARGs in smog for the potential health risk evaluation.