Zero valent iron (ZVI) has been previously documented to attenuate the propagation of antibiotic resistance genes (ARGs) in microbes, while how ZVI affects the evolution of ARGs remains unclear. Herein, we investigated the influences of ZVI on ARGs dissemination in anaerobic bioreactor treating oxytetracycline (tet) containing wastewater, by deciphering the roles of iron homeostasis and regulatory effects. A net reduction of tet gene targets ranging from 0.75 to 1.88 and 0.67 to 2.08 log unit in intracellular and extracellular DNA was achieved at the optimal dosage of 5 g/L ZVI, whereas 20 g/L ZVI made no effects on ARGs reduction. The reduced ARGs abundance by ZVI was directly related to the inhibited horizontal transfer of ARGs and decreased proliferation of resistant strains (mainly Paludibacter and WCHB1–32). The potential mechanisms included the increased antioxidant capacity, the depressed efflux pump system and the weakened energy driving force by Fur regulon in microbes (especially for Cloacibacterium and Dechloromonas). The negligible influence of 20 g/L ZVI on ARGs reduction was ascribed to the iron-catalyzed oxidative damage and reduced physiological activity. This study firstly illustrated the potential relationships among activation of iron uptake regulator leading to protection against oxidative stress, alternation of physiological metabolisms and reduction of ARGs dissemination. This work extents our understanding about the priority of ZVI in mitigating ARGs proliferation and sheds light on its potential application in wastewater treatment plants.

零价铁（ZVI）先前已被证明可减弱微生物中的抗生素抗性基因（ARGs）的传播，而ZVI如何影响ARGs的进化尚不清楚。在这里，我们通过研究铁稳态的作用和调节作用，研究了ZVI对厌氧生物反应器处理含氧四环素（tet）的厌氧生物反应器中ARGs传播的影响。净减少tet在5 g / L ZVI的最佳剂量下，细胞内和细胞外DNA的基因目标范围分别为0.75至1.88和0.67至2.08 log单位，而20 g / L ZVI对降低ARGs没有影响。ZVI降低的ARGs丰度与ARGs的水平转移抑制和耐药菌株（主要是Paludibacter和WCHB1-32）的增殖减少直接相关。潜在的机制包括增加的抗氧化能力，降低的外排泵系统以及Fur regulon对微生物的能量驱动力减弱（尤其是对于梭菌和脱氯单胞菌而言））。20 g / L ZVI对ARGs还原的影响可以忽略不计，这归因于铁催化的氧化损伤和生理活性的降低。这项研究首先阐明了铁吸收调节剂的激活与抗氧化应激的保护，生理代谢的改变以及ARGs传播减少之间的潜在关系。这项工作扩展了我们对ZVI在缓解ARGs扩散中的优先级的理解，并阐明了ZVI在废水处理厂中的潜在应用。