Microbial electrochemical composting reduced the risk of antibiotic resistance genes

Abstract

The use of livestock and poultry manure as fertilizer is the primary way for antibiotic resistance genes (ARGs) to enter agricultural soil; therefore it is crucial to reduce ARGs during composting. In this study, microbial fuel cells (MFCs) were employed to strengthen the removal of ARGs in composting. The results indicated that mobile genetic elements (MGEs) were the primary factors influencing ARGs, and the stimulation of biocurrent by MFCs effectively reduced the abundance of ARGs positively correlated with MGEs. Although the risk of vanS, bcrA and tetR were classified as III, IV and IV, respectively, these ARGs were found to have a high transmission risk. The abundances of vanS, bcrA and tetR showed the lowest in MFCs, with reductions of 22 %, 50 % and 21 %, respectively, compared to the control. Caudoviricetes exhibited significant ARG co-occurrence with six bacteria, particularly Bacteroidetes-Caudoviricetes and Firmicutes-Caudoviricetes, whose abundance was 52 % lower in MFCs than that in the open-circuit control. The abundance of potential human pathogenic bacteria (HPB) decreased by 37 % after electrode introduction, and further declined to 67 % with the stimulation of biocurrent. Besides, the correlation between ARGs and HPB decreased by 44 % after the introduction of electrodes, while no correlation was found between ARGs and HPB in MFCs. Overall, this study offered an efficient and safe solution for composting using electrochemical technology.