MOE Key Lab of Environmental Remediation and Ecosystem Health, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou, Zhejiang 310030, PR China.
MOE Key Lab of Environmental Remediation and Ecosystem Health, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou, Zhejiang 310030, PR China.
Sci Total Environ. 2023 Oct 20;896:165219. doi: 10.1016/j.scitotenv.2023.165219. Epub 2023 Jun 29.
Inorganic arsenic and organochlorines are frequently co-occurring contaminants in anoxic groundwater environments, and the bioremediation of their composite pollution has long been a rigorous predicament. Currently, the dechlorination behaviors and stress responses of microbial dechlorination consortia to arsenic are not yet fully understood. This study assessed the reductive dechlorination performance of a Dehalococcoides-bearing microcosm DH under gradient concentrations of arsenate [As(V)] or arsenite [As(III)] and investigated the response patterns of different functional microorganisms. Our results demonstrated that although the dechlorination rates declined with increasing arsenic concentrations in both As(III/V) scenarios, the inhibitory impact was more pronounced in As(III)-amended groups compared to As(V)-amended groups. Moreover, the vinyl chloride (VC)-to-ethene step was more susceptible to arsenic exposure compared to the trichloroethene (TCE)-to-dichloroethane (DCE) step, while high levels of arsenic exposure [e.g. As(III) > 75 μM] can induce significant accumulation of VC. Functional gene variations and microbial community analyses revealed that As(III/V) affected reductive dechlorination by directly inhibiting organohalide-respiring bacteria (OHRB) and indirectly inhibiting synergistic populations such as acetogens. Metagenomic results indicated that arsenic metabolic and efflux mechanisms were identical among different Dhc strains, and variations in arsenic uptake pathways were possibly responsible for their differential responses to arsenic exposures. By comparison, fermentative bacteria showed high potential for arsenic resistance due to their inherent advantages in arsenic detoxification and efflux mechanisms. Collectively, our findings expanded the understanding of the response patterns of different functional populations to arsenic stress in the dechlorinating consortium and provided insights into modifying bioremediation strategies at co-contaminated sites for furtherance.
无机砷和有机氯是缺氧地下水环境中经常共存的污染物，其复合污染的生物修复长期以来一直是一个严峻的难题。目前，微生物脱卤菌群对砷的脱卤行为和应激反应尚不完全清楚。本研究评估了含有 Dehalococcoides 的微宇宙 DH 在砷酸盐[As(V)]或亚砷酸盐[As(III)]梯度浓度下的还原脱氯性能，并研究了不同功能微生物的响应模式。我们的结果表明，尽管在 As(III/V)两种情况下，随着砷浓度的增加，脱氯率都有所下降，但在添加 As(III)的组中，抑制作用比添加 As(V)的组更为明显。此外，与三氯乙烯(TCE)到二氯乙烷(DCE)的步骤相比，氯乙烯(VC)到乙烯的步骤对砷的暴露更为敏感，而高浓度的砷暴露[例如 As(III) > 75 μM]会导致 VC 的显著积累。功能基因变化和微生物群落分析表明，As(III/V)通过直接抑制有机卤化物呼吸细菌(OHRB)和间接抑制协同种群，如产乙酸菌，影响还原脱氯。宏基因组学结果表明，砷的代谢和外排机制在不同的 Dhc 菌株中是相同的，而砷摄取途径的变化可能是它们对砷暴露产生不同反应的原因。相比之下，由于其在砷解毒和外排机制方面的固有优势，发酵细菌表现出很高的砷抗性潜力。总的来说，我们的研究结果扩展了对脱卤菌群中不同功能种群对砷应激反应模式的认识，并为进一步修改复合污染场地的生物修复策略提供了思路。
