Calamus-based biochar filler enhanced wetlands mitigate antibiotic resistance risks: insight from metagenomics

In this study, an innovative phosphate-modified calamus-biochar (PBC) filler with high antibiotic adsorption capacity was developed to enhance constructed wetlands (CWs) wastewater treatment. Results showed that the erythromycin (ERY) and sulfamethoxazole (SMX) removal efficiency of PBC-CW was 86.5% and 84.0%, which was 2-fold higher than those of the blank group. Metagenomic analysis found that the ERY and SMX would significantly promote the increase in abundance of antibiotic resistance genes (ARGs), mobile genetic elements (MGEs) and virulence factor genes (VFGs). Compared to blank group, the abundances of ARGs, MGEs and VFGs were reduced by 51.3%, 33.3% and 11.2% in PBC-CW. Among them, the abundance of sulfonamide and MLS, which were key genes to resistance to SMX and ERY, respectively, were reduced by 71.8% and 63.1% in PBC-CW. Moreover, these persistent ARG subtypes, detected simultaneously in all the samples, reduced the total abundance by 44.8%. In addition, microbial community analysis found that the sum abundance of Arenimonas, Chryseobacterium and Hydrogenophaga, which were suggested as potential ARBs via correlation analysis, were significantly decreased from 1.54% in blank group to 0.23% in PBC group. Moreover, Chryseobacterium and Hydrogenophaga were positively correlated with VFGs, they could be pathogens with resistance genes. Therefore, PBC-CW could effectively reduce the abundance of ARGs and pathogenic microorganisms, thereby improving water security.