Thioredoxin-mediated sulfur cycling and biogenic sulfur encapsulation synergistically enhance co-removal of nitrogen, sulfamethoxazole, and resistance genes in constructed wetlands

Area of Science:

• Environmental Science
• Environmental Engineering
• Microbiology

Background:

• Constructed wetlands (CWs) face challenges balancing sulfur-driven denitrification with antibiotic resistance genes (ARGs) proliferation.
• Sulfide accumulation in CWs can compromise microbial integrity despite enhancing nitrogen removal.

Purpose of the Study:

• To engineer a novel FeS₂@S⁰ composite filler for constructed wetlands.
• To investigate the synergistic effects of thioredoxin (Trx)-mediated sulfur cycling and biogenic sulfur (bio-S⁰) encapsulation.
• To resolve the conflict between nitrogen removal and ARGs proliferation in CWs.

Main Methods:

• Engineered a FeS₂@S⁰ composite filler with specific crystal facets and sulfur vacancies.
• Investigated Trx-mediated conversion of sulfide to bio-S⁰ and its role in microbial adhesion.
• Analyzed the generation of reactive oxygen species (ROS) from sulfur vacancies for ARG degradation.
• Assessed nitrogen removal, sulfamethoxazole degradation, and ARG abundance reduction.

Main Results:

• The FeS₂@S⁰ system upregulated trxA/B genes, enhancing microbial adhesion and protecting denitrifiers.
• Sulfur vacancies generated ROS, degrading 73.00% of EPS-bound ARGs and suppressing horizontal gene transfer.
• Achieved 68.66% total nitrogen removal and 50.17% sulfamethoxazole degradation, outperforming conventional substrates.
• Reduced ARG abundance by 61.24-67.31% and minimized H₂S emissions.

Conclusions:

• The engineered FeS₂@S⁰ filler establishes a self-sustaining sulfur cycle, enhancing CW performance.
• This approach enables simultaneous nitrogen retention, antibiotic degradation, and ARGs suppression.
• Redefines CWs as robust systems for sustainable wastewater treatment.