Globally occurring nitrate pollution in groundwater is harming the environment and human health. In situ hydrogen addition to stimulate denitrification has been proposed as a remediation strategy. However, observed nitrite accumulation and incomplete denitrification are severe drawbacks that possibly stem from the specific microbial community composition. We set up a microcosm experiment comprising sediment and groundwater from a nitrate polluted oxic oligotrophic aquifer. After the microcosms were sparged with hydrogen gas, samples were taken regularly within 122 h for nitrate and nitrite measurements, community composition analysis via 16S rRNA gene amplicon sequencing, and gene and transcript quantification via qPCR of reductase genes essential for complete denitrification. The highest nitrate reduction rates and greatest increase in bacterial abundance coincided with the 15.3-fold increase in Rhodocyclaceae, specifically six ASVs that are closely related to the genus Dechloromonas. The denitrification reductase genes napA, nirS, and clade I nosZ also increased significantly over the observation period. We conclude that taxa of the genus Dechloromonas are the prevailing hydrogenotrophic denitrifiers in this nitrate polluted aquifer and the ability of hydrogenotrophic denitrification under the given conditions is species-specific.

中文翻译：

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在含氧含水层物质刺激的微观世界中，脱氯monas和近亲占优势的氢营养反硝化作用

全球范围内发生的地下水硝酸盐污染正在危害环境和人类健康。原位已经提出添加氢来刺激反硝化作为补救策略。但是，观察到的亚硝酸盐积累和不完全反硝化是严重的缺陷，可能源自特定的微生物群落组成。我们建立了一个缩影实验，包括硝酸盐污染的缺氧贫营养含水层中的沉积物和地下水。在用氢气喷射微观世界后，定期在122小时内取样以进行硝酸盐和亚硝酸盐测量，通过16S rRNA基因扩增子测序进行群落组成分析，以及通过qPCR对完全脱氮必不可少的还原酶基因进行基因和转录本定量。最高的硝酸盐还原速率和最大的细菌丰度增加与杜鹃花科的15.3倍增加相吻合，特别是六个与绿藻属密切相关的ASV。在观察期内，反硝化还原酶基因napA，nirS和进化枝I  nosZ也显着增加。我们得出结论，在该硝酸盐污染的含水层中，Dechloromonas属的类群是主要的氢营养反硝化剂，在给定条件下氢营养反硝化的能力是特定于物种的。