Insights into the response of nitrogen metabolism to sulfamethoxazole contamination in constructed wetlands with varied substrates.

[Display omitted] • Nitrogen removal efficiencies by zeolite wetland was better than ceramists and lava. • Selective inhibition of amo B and hao gene abundance on different substrates. • Denitrification is a key pathway for nitrate removal in constructed wetland (CW) • Dissimilatory nitrate reduction process was enhanced in CW- zeolite. This study conducted an analysis of the variations in nitrogen metabolism pathways within constructed wetlands (CWs) using zeolite (CW-Z), ceramsite (CW-C), and lava (CW-L) under high concentration sulfamethoxazole (SMX) stress. The introduction of SMX hindered the formation of hydrogen bonds on the substrate surfaces; however, these surfaces still maintained a dense and thick biofilm. CW-Z exhibited superior removal efficiencies for ammonium nitrogen (NH 4 +-N) and nitrate nitrogen (NO 3 –-N) compared to CW-C and CW-L, with removal rates of 92.54 ± 2.88 % and 89.39 ± 6.74 %, respectively. Interestingly, the proportion of genes involved in nitrification, denitrification and nitrate reduction genes in CW-C (36.05 %) were higher than that in CW-C (29.81 %) and CW-L (29.70 %) but the interactions among nitrogen functional bacteria in CW-Z were much more complex. Further analysis of the nitrogen metabolism pathway indicated that under CW-Z enhanced dissimilatory nitrate reduction SMX stress, while CW-L enhanced assimilatory nitrate reduction process compared to CW-C. [ABSTRACT FROM AUTHOR]