School of Environmental Science and Engineering, Sun Yat-Sen University, Guangzhou 510275, China; Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology (Sun Yat-Sen University), Guangzhou 510275, China; Guangdong Water Co., Ltd., Shenzhen 518021, China.
School of Environmental Science and Engineering, Sun Yat-Sen University, Guangzhou 510275, China; Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology (Sun Yat-Sen University), Guangzhou 510275, China.
Water Res. 2023 Nov 1;246:120753. doi: 10.1016/j.watres.2023.120753. Epub 2023 Oct 18.
Incomplete mineralization of sulfamethoxazole (SMX) in wastewater treatment systems poses a threat to ecological health. The toxicity and environmental risk associated with SMX biodegradation in the sulfur-mediated biological process were examined for the first time through a long-term (180 days) bioreactor study and a series of bioassays. The results indicated that the sulfur-mediated biological system was highly resistant and tolerant to SMX toxicity, as evidenced by the enrichment of sulfate-reducing bacteria (SRB), the improved microbial metabolic activity, and the excellent performance on pollutants removal under long-term SMX exposure. SMX can be effectively biodegraded by the cleavage and rearrangement of the isoxazole ring, hydrogenation and hydroxylation reactions in sulfur-mediated biological wastewater system. These biodegradation pathways effectively reduced the acute toxicity, antibacterial activity, and ecotoxicities of SMX and its biotransformation products (TPs) in the effluent of the sulfur-mediated biological system. The TPs produced via hydrogenation (TP1), hydroxylation, and isoxazole ring cleavage (TP3, TP4, TP5, TP8, and TP9) exhibited lower toxicity than SMX. Under SMX stress, although the abundance of sulfonamide resistance genes increased, the total abundance of ARGs decreased due to the extrusion of some intracellular SMX by the efflux pump genes and the inactivation of some SMX through the biodegradation process. Efflux pump and inactivation, as the main resistance mechanisms of antibiotics in the sulfur-mediated biological system, play a crucial role in microbial self-defense. The findings of this study demonstrate the great potential of the sulfur-mediated biological system in SMX removal, detoxication, and ARGs environmental risk reduction.
在废水处理系统中，磺胺甲恶唑（SMX）的不完全矿化对生态健康构成威胁。本研究首次通过长期（180 天）生物反应器研究和一系列生物测定，考察了 SMX 在硫介导的生物过程中生物降解的毒性和环境风险。结果表明，硫介导的生物系统对 SMX 毒性具有很强的抗性和耐受性，这表现为硫酸盐还原菌（SRB）的富集、微生物代谢活性的提高以及在长期 SMX 暴露下对污染物去除的优异性能。SMX 可以通过硫介导的生物废水系统中环的裂解和重排、氢化和羟化反应有效地进行生物降解。这些生物降解途径有效地降低了 SMX 及其生物转化产物（TPs）在硫介导的生物系统出水中的急性毒性、抗菌活性和生态毒性。通过氢化（TP1）、羟化和异恶唑环裂解产生的 TPs（TP3、TP4、TP5、TP8 和 TP9）的毒性低于 SMX。在 SMX 胁迫下，尽管磺胺类耐药基因的丰度增加，但由于外排泵基因将一些细胞内 SMX 挤出和一些 SMX 通过生物降解过程失活，总 ARGs 丰度下降。外排泵和失活作为抗生素在硫介导的生物系统中的主要耐药机制，在微生物自我防御中起着至关重要的作用。本研究结果表明，硫介导的生物系统在 SMX 去除、解毒和降低 ARGs 环境风险方面具有巨大潜力。
