State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Wuhan 430074, PR China.
State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Wuhan 430074, PR China.
Sci Total Environ. 2020 Sep 15;735:139501. doi: 10.1016/j.scitotenv.2020.139501. Epub 2020 May 19.
The factors that control arsenic (As) mobilization by dissimilatory iron reduction (DIR) are complicated. The association between As mobilization and extracellular polymeric substance (EPS) of dissimilatory iron reducing bacteria (DIRB) remained unclear. In this study, three DIRB were isolated from high arsenic groundwater to understand the effects of EPS on As mobilization. In the laboratory settings, strain Klebsiella oxytoca IR-ZA released As into aqueous phase from As-bearing ferrihydrite, while strain Shewanella putrefaciens IAR-S1 and S. xiamenensis IR-S2 re-sequestrated As by forming secondary minerals during ferrihydrite reduction. Characterization of EPS contents with Fourier Transform Infrared Spectroscopy and high-performance liquid chromatography suggested that mannan and succinic acid were the main different EPS contents of the DIRB. The biomineralization processes were tightly regulated by EPS compositions. Mannan secreted by IAR-S1 and IR-S2 promoted while succinic acid secreted by IR-ZA suppressed the biomineralization and As immobilization. Energy-dispersive X-ray Spectroscopy mapping indicated that As in the secondary minerals was wrapped with EPS. X-ray diffraction and room temperature Mössbauer spectroscopy showed these secondary minerals were vivianite and magnetite, respectively. The amount of As mobilized into aqueous phase was strongly affected by available anions (HPO and HCO). Our results indicated that the EPS of DIRB significantly influenced As mobilization.
异化铁还原（DIR）控制砷（As）迁移的因素很复杂。As 迁移与异化铁还原菌（DIRB）的胞外聚合物（EPS）之间的关联尚不清楚。在本研究中，从高砷地下水分离出三株 DIRB，以了解 EPS 对 As 迁移的影响。在实验室条件下，氧化葡萄糖酸杆菌 IR-ZA 将 As 从含砷的水铁矿中释放到水相，而施氏假单胞菌 IAR-S1 和厦门希瓦氏菌 IR-S2 在还原水铁矿的过程中通过形成次生矿物重新螯合 As。傅里叶变换红外光谱和高效液相色谱法对 EPS 含量的表征表明，甘露聚糖和琥珀酸是 DIRB 的主要不同 EPS 含量。生物矿化过程受到 EPS 组成的严格调控。IAR-S1 和 IR-S2 分泌的甘露聚糖促进了生物矿化和 As 固定，而 IR-ZA 分泌的琥珀酸则抑制了生物矿化和 As 固定。能谱 X 射线微区分析表明，次生矿物中的 As 被 EPS 包裹。X 射线衍射和室温穆斯堡尔光谱表明，这些次生矿物分别为磷铁矿和磁铁矿。进入水相的 As 迁移量受可用阴离子（HPO 和 HCO）的强烈影响。我们的结果表明，DIRB 的 EPS 显著影响 As 的迁移。
