Metagenomics Disentangles Differential Resistome Traits\nand Risks in Full-Scale Anaerobic Digestion Plants under Ambient,\nMesophilic, and Thermophilic Conditions

Anaerobic digestion\n(AD) systems are vital for converting organic\nwaste to green bioenergy but also serve as a non-negligible environmental\nreservoir for antibiotic-resistance genes (ARGs) and resistant bacteria\nof environmental and human health concerns. This study profiles the\nantibiotic resistome of 90 full-scale biogas reactors and reveals\nthat AD microbiomes harbor at least 30 types and 1257 subtypes of\nARGs, of which 16% are located on plasmids showing potential mobility.\nThe total abundance of AD-ARGs ranges widely from 0.13 to 7.81 copies\nper cell and is distributed into 42–739 subtypes, significantly\ninfluenced (<i>P</i> < 0.05) by operational conditions\nlike digestion temperature and substrate types. Compared with the\nambient and mesophilic digesters, the thermophilic digesters harbor\na significantly lower abundance and diversity as well as greatly reduced\nmobility and host pathogenicity levels (all <i>P</i> <\n0.05) of ARGs, revealing that a higher digestion temperature mitigates\nthe overall resistome risks. The comprehensive analysis of basic traits\nand key traits of the AD resistome is demonstrated to provide crucial\nquantitative and qualitative insights into the diversity, distribution\npattern, and health risks of ARGs in full-scale AD systems. The revealed\nknowledge offers new guidance for improving environmental resistome\nmanagement and developing oriented mitigation strategies to minimize\nthe unwanted spread of clinically important antimicrobial resistance\nfrom AD systems.