School of Environmental Studies, China University of Geosciences, Wuhan 430074, PR China.
School of Environmental Studies, 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. 2021 Aug 20;783:147002. doi: 10.1016/j.scitotenv.2021.147002. Epub 2021 Apr 9.
The reduction of Fe(III) by metal-reducing bacteria through extracellular electron transfer (EET) is a critical link in the biogeochemical cycle of As/Fe, and humic substances are believed to play a role in this process. In this study, the indigenous As-resistant bacterium Bacillus D2201 isolated from the Datong Basin was responsible for the valence transition of Fe and As in the groundwater environment. The bacterium has both the arsC gene for intracellular arsenate reduction and an EET pathway for transferring electrons to an electrode or Fe(III). Chronoamperometry showed that 3.0- and 10.2-fold increases in the output current density were achieved by injecting 0.05 and 0.5 mM AQDS with an inoculation of Bacillus D2201. Interestingly, Fe(III) bio-reduction is not only regulated by AQDS, but also by As(V) stimulation. The increase in pyruvate consumption and levels of intracellular glutathione (GSH) suggest that As pressure promotes cell metabolism and the consumption of electron donors for Fe(III) reduction with strain D2201. The reduction and dissolution of Fe(III) mineral regulated by AQDS dominated the release and mobilization of As. Compared with the AQDS-free treatment, 5.5-, 6.6-, and 7.2-fold increases in the amounts of Fe(II) were released with the addition of 0.1, 0.5, and 1 mM AQDS, respectively, and approximately 2.6-, 2.8-, and 3.2-fold increases in the As(V) levels were observed under the same conditions. These insights have profound environmental implications with respect to the effect of AQDS and As stress on EET and Fe(III) reduction in arsenic-resistant bacteria.
铁还原菌通过胞外电子传递（EET）将 Fe(III)还原是砷/铁生物地球化学循环的关键环节，而腐殖质被认为在此过程中发挥作用。在这项研究中，从大同盆地分离出的耐砷菌 Bacillus D2201 负责地下水环境中 Fe 和 As 的价态转变。该菌同时具有细胞内砷酸盐还原的 arsC 基因和将电子传递到电极或 Fe(III)的 EET 途径。计时安培法表明，当接种 Bacillus D2201 并注入 0.05 和 0.5 mM 的 AQDS 时，输出电流密度分别提高了 3.0 和 10.2 倍。有趣的是，Fe(III)的生物还原不仅受 AQDS 调节，还受 As(V)的刺激调节。丙酮酸消耗和细胞内谷胱甘肽 (GSH)水平的增加表明，As 压力促进了细胞代谢和电子供体的消耗，以用于 D2201 菌株的 Fe(III)还原。AQDS 调节的 Fe(III)矿物的还原和溶解主导着 As 的释放和迁移。与无 AQDS 处理相比，添加 0.1、0.5 和 1 mM AQDS 时，分别释放出 5.5、6.6 和 7.2 倍的 Fe(II)，在相同条件下，As(V)水平分别增加了 2.6、2.8 和 3.2 倍。这些发现对于 AQDS 和 As 胁迫对 EET 和耐砷菌中 Fe(III)还原的影响具有深远的环境意义。
