Influence of wastewater antibiotic resistance difference on horizontal gene transfer risk using electrochemical flow-through reaction

Wastewaters from different sources are complex reservoirs for the emergence and spread of antibiotic resistance genes (ARGs). At present, there is no systematically comparative study on the characteristics of water quality, microbial community, and horizontal gene transfer (HGT) risk in different wastewaters. This study collected four wastewaters to compare the removal of antibiotics; the relative abundances of host bacteria, ARGs, and mobile genetic elements (MGEs); the microbial community; and HGT risks after electrochemical flow-through reaction (EFTR) process. Metagenomic sequencing analysis indicated that the relative abundance of ARGs decreased except for multidrug resistance genes and that of MGEs increased in different wastewaters after EFTR treatment. The extremely high efficiency of variation in the relative abundances of ARGs and MGEs resulted in a higher possibility of ARGs being encoded in chromosomes in surface water (SW) compared with other wastewaters. Meanwhile, the composition of bacterial community and the relative abundance of host bacteria had remarkable differences in different wastewaters. Moreover, the functional genes related to oxidative stress and DNA damage response (SOS response) were triggered in different wastewaters in varying degrees by EFTR treatment and affected the spread of ARGs. The livestock wastewater after biological treatment process (LW) had the highest proportion and lowest removal efficiency of ARGs located on the plasmid compared with other wastewaters, which increased the HGT risk. This study provided a foundation for wastewater treatment and ARGs transfer control.