Key Laboratory of Industrial Ecology and Environmental Engineering, School of Environment Science and Technology, Dalian University of Technology, Dalian 116024, China.
Key Laboratory of Industrial Ecology and Environmental Engineering, School of Environment Science and Technology, Dalian University of Technology, Dalian 116024, China.
Sci Total Environ. 2022 Mar 1;810:151184. doi: 10.1016/j.scitotenv.2021.151184. Epub 2021 Oct 24.
Microbial remediation provides a promising avenue for the management and restoration of heavy metal-contaminated soils. Microorganisms in soils usually exist within unsaturated biofilms, however, their response to heavy metals is still limited compared to saturated biofilms. This work investigated the Cr(VI) immobilization by Shewanella putrefaciens CN32 unsaturated biofilms, and explored the underlying mechanisms of Cr(VI) complexation. Results reveal a dose-dependent toxicity of Cr(VI) to the growth of the unsaturated biofilms. During the early growth stage, the Cr(VI) addition stimulated more extracellular polymeric substances (EPS) production. In the meantime, the EPS were demonstrated to be the primary components for Cr(VI) immobilization, which accounted for more than 60% of the total adsorbed Cr(VI). The Fourier transform infrared spectra and X-ray photoelectron spectra corroborated that the binding sites for immobilizing Cr(VI) were hydroxyl, carboxyl, phosphoryl and amino functional groups of the proteins and polysaccharides in EPS. However, for the starved unsaturated biofilms, EPS were depleted and the EPS-bound Cr(VI) were released, which caused approximately 60% of the adsorbed Cr(VI) onto cell components and further aggravated the Cr(VI) stress to cells. This work extends our understanding about the Cr(VI) immobilization by unsaturated biofilms, and provides useful information for remediation of heavy metal-contaminated soils.
微生物修复为重金属污染土壤的管理和修复提供了一条有前景的途径。土壤中的微生物通常存在于不饱和生物膜中，然而，与饱和生物膜相比，它们对重金属的响应仍然有限。本研究调查了 Shewanella putrefaciens CN32 不饱和生物膜对 Cr(VI)的固定作用，并探讨了 Cr(VI)络合的潜在机制。结果表明，Cr(VI)对不饱和生物膜的生长具有剂量依赖性毒性。在早期生长阶段，Cr(VI)的添加刺激了更多的胞外聚合物（EPS）的产生。同时，EPS 被证明是 Cr(VI)固定的主要成分，占总吸附 Cr(VI)的 60%以上。傅里叶变换红外光谱和 X 射线光电子能谱证实，固定 Cr(VI)的结合位点是 EPS 中蛋白质和多糖的羟基、羧基、磷酸基和氨基官能团。然而，对于饥饿的不饱和生物膜，EPS 被耗尽，EPS 结合的 Cr(VI)被释放，这导致大约 60%的吸附 Cr(VI)转移到细胞成分上，进一步加重了 Cr(VI)对细胞的胁迫。这项工作扩展了我们对不饱和生物膜固定 Cr(VI)的理解，并为重金属污染土壤的修复提供了有用的信息。
