Metagenomic approach reveals the fate of antibiotic resistance genes in a temperature-raising anaerobic digester treatingmunicipal sewage sludge Raw sequence reads. Metagenomic approach reveals the fate of antibiotic resistance genes in a temperature-raising anaerobic digester treatingmunicipal sewage sludge

The fate of diverse antibiotic resistance genes (ARGs) inanaerobic digestion (AD) system under different temperature remains largely unknow. This study investigatedthe shifts of composition and abundance of more than 1360 ARGs, as well as microbial community, in a temperature-raising AD system treating municipal sewage sludgemetagenomic sequencing, by the combination of 16S rRNA amplicon sequencing and bioinformatic analysis.Results showed that macB (one macrolideantibiotic resistance gene) was predominant in all samples (7.9%-8.7%) and more than 98% ARGs were detected to be less than 1%. Thermophilic AD provided superior removal for ARGs when compared with mesophilic AD. Genes encoding tetracycline, macrolide, penam, fluoroquinolone, acridine dye, and peptide antibiotic resistance were dominated in sludge samples and could be removed by 29.7%-32.2% with the digestion temperature increased from mesophilic to theomorphic condition. This study further proposed the underlying mechanisms of effective eliminationof ARGs under high temperature by: (1) the inactivation of multidrug-resistant bacteria, (2) the reduction of genes encoding antibiotic efflux pump, (3) the promotion of sludge biomassdegradation rate, and (4) the loss of microbial communitydiversity in AD systems. The significance of current study is in comprehensively understanding the fate of ARGs across AD process, which will allow the manipulation of AD technology (e.g. temperature) to efficiently remove ARGs from municipal sewagesludge.