Antibiotic resistome alteration along a full-scale drinking water supply system deciphered by metagenome assembly: Regulated by seasonality, mobile gene elements and antibiotic resistant gene hosts

Both drinking water treatment processes and distribution can lead to antibiotic resistome variation, yet the variation ofantibiotic resistome in the whole drinking water supply system (DWSS) combined with seasonality remains unknown.In this study, microbial community, antibiotic resistome, mobile genetic elements (MGEs) co-existing with antibioticresistance genes (ARGs) and ARG hosts would be explored along a DWSS for four seasons with metagenome assembly.Multidrug and bacitracin ARGs were dominant ARGs in DWSS. Integrase, plasmids, recombinase and transposase weremajor MGEs co-existing with ARGs. Filtration and disinfection treatments could alter the ARG relative abundance,mainly via changing the abundance of ARG hosts (LimnohabitansandPolynucleobacter), which was influenced bywater total organic carbon (TOC) content. When TOC was relatively high,filtration could proliferate ARGs via promot-ing antibiotic resistance bacteria (ARB) but chlorine dioxide could decrease ARGs via killing ARB. Filtration played animportant role in controlling ARGs by reducing ARB when TOC was relatively low. The stimulation effect of disinfec-tion on ARGs existed in more oligotrophic environment. Distribution could enrich ARGs in higher temperature byincreasing MGEs co-occurring with ARGs and diversifying ARG hosts. MGEs co-occurring with ARGs became moreabundant and diverse in disinfected water in warmer seasons. Microbial community was the most important factordetermining the antibiotic resistome along a DWSS. Thesefindings extend the knowledge about how and whywater treatment processes and pipe distribution shape drinking water antibiotic resistome in different seasons

Automated summary

This study explores the variation of antibiotic resistome in the drinking water supply system (DWSS) combined with seasonality. The dominant antibiotic resistance genes (ARGs) in DWSS are multidrug and bacitracin ARGs. Mobile genetic elements (MGEs) such as integrase, plasmids, recombinase, and transposase co-exist with ARGs. Filtration and disinfection treatments can alter the abundance of ARGs by changing the abundance of ARG hosts influenced by water total organic carbon (TOC) content.