School of Environmental Studies, China University of Geosciences, Wuhan 430074, China.
State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Wuhan 430074, China.
Int J Environ Res Public Health. 2022 Aug 4;19(15):9606. doi: 10.3390/ijerph19159606.
Arsenic (As) mobilization in groundwater involves biogeochemical cycles of carbon, iron, and sulfur. However, few studies have focused on the role of nitrogen-metabolizing bacteria in As mobilization, as well as in the transformation between inorganic and organic As in groundwater. In this study, the nitrogen and As metabolisms of sp. G-C1 and sp. G-11, isolated from high As groundwater in Hetao Plain, China, were characterized by culture experiments and genome sequencing. The results showed sp. G-C1 was a dissimilatory nitrate-reducing bacterium. The dissimilatory nitrate reduction to ammonia (DNRA) and As-detoxifying pathways identified in the genome enabled sp. G-C1 to simultaneously reduce As(V) during DNRA. sp. G-11 was a nitrogen-fixing bacterium and its nitrogen-fixing activity was constrained by As. Nitrogen fixation and the As-detoxifying pathways identified in its genome conferred the capability of As(V) reduction during nitrogen fixation. Under anaerobic conditions, sp. G-C1 was able to demethylate organic As and sp. G-11 performed As(III) methylation with the gene. Collectively, these results not only evidenced that ammonium-generating bacteria with the operon were able to transform As(V) to more mobile As(III) during nitrogen-metabolizing processes, but also involved the transformation between inorganic and organic As in groundwater.
砷（As）在地下水中的迁移涉及碳、铁和硫的生物地球化学循环。然而，很少有研究关注氮代谢细菌在砷迁移以及地下水中无机和有机砷之间转化中的作用。本研究通过培养实验和基因组测序，对从中国河套平原高砷地下水中分离得到的 sp. G-C1 和 sp. G-11 的氮素和砷代谢进行了研究。结果表明，sp. G-C1 是一种异化硝酸盐还原菌。基因组中鉴定出的异化硝酸盐还原为氨（DNRA）和砷解毒途径使 sp. G-C1 能够在 DNRA 过程中同时还原 As(V)。sp. G-11 是一种固氮菌，其固氮活性受到 As 的限制。基因组中鉴定出的固氮作用和砷解毒途径赋予了其在固氮过程中还原 As(V)的能力。在厌氧条件下，sp. G-C1 能够脱甲基有机砷，而 sp. G-11 则通过基因进行 As(III)甲基化。总的来说，这些结果不仅证明了具有 操纵子的产铵细菌能够在氮代谢过程中将 As(V)转化为更具迁移性的 As(III)，还涉及到地下水中无机和有机砷之间的转化。
