摘要

       厌氧消化池中的生物硫化物（BS）被认为是通过M-NPs的硫化作用来减轻金属纳米粒子（M-NPs）对耐药基因（ARGs）增殖的潜在影响。本文报道了BS在调节精氨酸对M-NPs反应中的新作用。结果表明，环境相关水平的CuO纳米颗粒对ARGs的扩散没有显著影响。然而，较高的剂量（50mg/gTSS）有助于ARGs的繁殖，如果刺激BS的产生，ARGs的丰度将有效降低74-115%。相反，金属离子螯合剂EDTA的引入导致了较低的衰减效率（12-40%），这表明限制CuO纳米粒的生物利用度可能不是在BS存在下缓冲ARG反应的唯一原因。进一步的研究表明，BS的存在和关键酶（O-乙酰丝氨酸巯基化酶和γ-谷氨酰半胱氨酸合成酶）的激活有利于半胱氨酸的合成和转化，从而减轻CuO-NPs诱导的氧化应激。污泥中半胱氨酸及其代谢产物谷胱甘肽含量与ARGs含量呈负相关，说明原位生成的半胱氨酸是ARGs的重要调节因子。对可能的机制的探讨表明，生物合成的半胱氨酸可能通过移动基因元件限制基因转移的潜力，因为半胱氨酸限制了intI 1、Tn916/1545和iscr1的丰度。此外，半胱氨酸显著缓解了铜胁迫和铜抗性，从而阻断了铜与抗生素抗性之间可能的协同选择。这项工作为消化池中纳米粒生物效应的衰减提供了新的见解。

       Biogenic sulfide (BS) in anaerobic digesters was previously suggested to mitigate the potential impacts of metallic nanoparticles (M-NPs) on antibiotic resistance genes (ARGs) propagation by sulfidation of the M-NPs. In this study, a new role of BS in regulating ARGs responses to M-NPs is reported. It was observed that CuO NPs at environmentally relevant level had no significant effects on the spread of ARGs. However, higher dosage (50 mg/gTSS) contributed to the propagation of ARGs, whose abundances would be effectively reduced by 74-115% if BS production was stimulated. Instead, introduction of EDTA, a metal ion chelator, resulted in much lower attenuation efficiencies (12-40%), indicating that restriction of the bioavailability of CuO NPs might not be the only reason for the buffering of ARG responses in the presence of BS. Further investigation showed that the presence of BS together with activation of key enzymes (O-acetyl serine sulfhydrylase and γ-glutamylcysteine synthetase) supplied and favored the biosynthesis and transformation of cysteine, which mitigated the oxidative stress induced by CuO NPs. Moreover, the amounts of cysteine and its metabolite glutathione in sludge were associated with the abundances of ARGs negatively, implying that in situ generated cysteine was the important ARGs regulator. Exploration of possible mechanisms revealed that the biosynthesized cysteine might limit gene transfer potential via mobile genetic elements, as cysteine restricted the abundances of intI 1, Tn916/1545 and ISCR 1. In addition, the cysteine remarkably alleviated the copper stress and copper resistance, which in turn blocked possible co-selection between copper and antibiotic resistance. This work provides new insight into attenuation of the bio-effects of NPs in digesters.

        https://www.sciencedirect.com/science/article/abs/pii/S0043135419303276?via%3Dihub