Dissemination of size-fractionated antibiotic resistance genes

The prevalence of antibiotic resistance genes (ARGs) and opportunistic pathogens are great threat to public health. However, the dissemination of ARGs and opportunistic pathogens in free-living (FL) or particle attached (PA) bacteria in water environments is less explored. Here, we explored the seasonal distribution of size-fractionated ARGs and opportunistic pathogens in the Yellow River by high-throughput quantitative PCR techniques and 16S rRNA gene sequencing. Water quality parameters and heavy metal content were also detected by physiochemical analysis. The PA-ARGs had higher absolute abundance than FL-ARGs in the Yellow River regardless of seasons. Both PA-ARGs and FL-ARGs had highest absolute abundance and diversity in winter. Mobile genetic element (MGE) was the dominant driver for both size-fractionated ARGs. However, environmental factors could influence PA-ARG profiles rather than FL-ARG profiles. Both FL-ARG and PA-ARG community assembly can be explained by neutral processes. It is noted that some opportunistic pathogens Aeromonas and Pseudomonas may be potential hosts for ARGs, and they also exhibited higher relative abundance in a free-living lifestyle rather than particle attached. Thus, it is vital to distinguish the ARGs and opportunistic pathogens from size-fractionated bacteria, and then make some targeted strategies to manage the dissemination of ARGs and opportunistic pathogens for public health.