Particulate matter continuum as distinct colonization niches for antibiotic resistome, mobilome and virulence factor genes in wastewater: Insights from full size-fractionated partitioning.

Particulate matter continuum is recognized for its significant role as a colonization niche for microorganisms, along with antibiotic resistome, mobilome, and virulence factor genes (VFGs). However, potential particle size effects on the dynamics of these bioactive pollutants in WWTPs is largely unknown. Hence, we used filtration membranes to fractionate particulate matter in wastewater into five size-fractions (< 0.2, 0.2 - 0.8, 0.8 - 3.0, 3.0 - 10.0, > 10.0 μm). The results showed that the diversity and abundances of antibiotic resistance genes (ARGs) and VFGs varied across these fractions. Notably, the particle range of 0.8 - 3.0 μm exhibited the highest relative abundances of ARGs (0.71) and MGEs (0.41), indicating that this size-fraction was their hotspots. Moreover, the relative abundances of phyla, such as Acidobacteria (0 - 11.73 %), Chloroflexi (0 - 11.03 %) and Patescibacteria (0.033 - 35.95 %) varied across the size-fractions. The differentiation of ARGs might be attributed to the diversity and structures of bacterial communities colonizing in different size-fractions. Furthermore, it was revealed that the size-fractions (< 3.0 μm) cannot be effectively removed by the treatment units. The removal efficiencies of size-fractionated ARGs are treatment process-specific. It highlights the need to adopt specific technologies to remove size-fractionated ARGs.