Fate of antibiotic resistance genes during temperature-changed psychrophilic anaerobic digestion of municipal sludge

The effects of anaerobic digestion (AD) on the abundance of antibiotic resistance genes (ARGs) are highly related to operational temperature. However, the removal performance of ARGs in psychrophilic AD and changed temperatures simulating variable seasonal temperatures is poorly understood. Herein, we inves-tigated the fate of ARGs, correlated bacterial communities and physicochemical properties of AD opera-tion at psychrophilic (15 degrees C), mesophilic (35 degrees C), and temperature changed conditions (15 to 35 degrees C and 35 to 15 degrees C). The results indicated that ammonia release was positively correlated with temperature. The mesophilic AD facilitated phosphorous intake and ARGs proliferation and selection with oxytetracycline (OTC), while psychrophilic AD was conducive to the removal and control of ARGs if no OTC existed. The diversity and composition of AD bacterial communities were influenced more by temperature than OTC. The dominant genera like Candidatus_Microthrix and Acinetobacter had dramatical abundance discrepan-cies at different temperatures and were obviously positively correlated with ARGs (tet39, tetC and mexD), mobile genetic elements (MGEs) intI, insert sequences (IS) and plasmid. The physicochemical properties of AD influenced the bacterial richness, which in turn significantly correlated with the ARGs abundances. Therefore, ARGs removal could be potentially optimized by eliminating bacterial hosts with deteriorated living conditions and decreased nutrients. This study clarified the response of antibiotic resistome to dif-ferent temperature variation and highlighted the potential strategies for improved ARGs removal in AD. (C) 2021 Elsevier Ltd. All rights reserved.

Automated summary

This study revealed that the removal efficiency of ARGs in anaerobic digestion (AD) is highly influenced by operational temperature, with psychrophilic AD showing potential for ARGs elimination in the absence of oxytetracycline. The diversity and composition of AD bacterial communities are more affected by temperature than oxytetracycline. The physicochemical properties of AD impact bacterial richness, which in turn significantly correlates with the abundances of ARGs.