Beijing Key Laboratory for Source Control Technology of Water Pollution, Engineering Research Center for Water Pollution Source Control and Eco-remediation, Beijing Forestry University, Beijing 100083, China.
Beijing Key Laboratory for Source Control Technology of Water Pollution, Engineering Research Center for Water Pollution Source Control and Eco-remediation, Beijing Forestry University, Beijing 100083, China.
Sci Total Environ. 2022 Aug 20;835:155301. doi: 10.1016/j.scitotenv.2022.155301. Epub 2022 Apr 13.
Sewage sludge has a high concentration of dissolved organic matter (DOM) which contains compounds that can serve as electron donors or shuttles for metal reduction by dissimilatory metal reducing bacteria (DMRB). In this study, Cr(VI) removal by G. sulfurreducens, a common DMRB present in anaerobic soils, was examined in the presence or absence of sludge DOM. Two different types of sludge DOM were tested; composted sludge DOM (C-DOM) and anaerobically digested sludge DOM (A-DOM). Both sludge DOMs enhanced Cr(VI) reduction by G. sulfurreducens, but C-DOM was more effective likely because it had higher concentrations of humic substances that served as electron shuttles. Transcriptomic studies indicated that G. sulfurreducens utilizes several different mechanisms to tolerate chromium including extracellular Cr(VI) reduction and immobilization by outer membrane c-type cytochromes and electrically conductive pili, intracellular Cr(VI) reduction by triheme cytochromes and NAD(P)H FMN reductase proteins, and chromium efflux by several P-type ATPase and RND transporter proteins. Microscopy experiments also showed that Cr(III) crystals formed on the surface of the cells, indicating that extracellular Cr(VI) reduction and adsorption was involved in the chromium removal process. These results help provide insight into the potential use of sewage sludge as an additive to enhance the bioremediation of chromium contaminated soils.
污水污泥中含有高浓度的溶解有机物 (DOM)，其中包含的化合物可以作为电子供体或穿梭物，促进异化金属还原菌 (DMRB) 还原金属。在这项研究中，检查了常见的厌氧土壤中 DMRB-硫还原地杆菌 (G. sulfurreducens) 在存在或不存在污泥 DOM 的情况下对六价铬 (Cr(VI)) 的去除情况。测试了两种不同类型的污泥 DOM；堆肥污泥 DOM (C-DOM) 和厌氧消化污泥 DOM (A-DOM)。两种污泥 DOM 均增强了 G. sulfurreducens 对 Cr(VI) 的还原，但 C-DOM 更有效，可能是因为它含有更高浓度的作为电子穿梭物的腐殖质。转录组研究表明，G. sulfurreducens 利用几种不同的机制来耐受铬，包括细胞外 Cr(VI) 还原和外膜 c 型细胞色素和导电菌毛的固定化、三血红素细胞色素和 NAD(P)H FMN 还原酶蛋白的细胞内 Cr(VI) 还原，以及几种 P 型 ATPase 和 RND 转运蛋白的铬外排。显微镜实验还表明，Cr(III) 晶体在细胞表面形成，表明细胞外 Cr(VI) 还原和吸附参与了铬去除过程。这些结果有助于深入了解将污水污泥作为添加剂来增强受铬污染土壤的生物修复的潜力。
