Department of Genetics and Microbiology, Universitat Autònoma de Barcelona, Bellaterra, Cerdanyola del Vallès, 08193, Barcelona, Spain.
Department of Genetics and Microbiology, Universitat Autònoma de Barcelona, Bellaterra, Cerdanyola del Vallès, 08193, Barcelona, Spain.
Chemosphere. 2021 Dec;285:131500. doi: 10.1016/j.chemosphere.2021.131500. Epub 2021 Jul 9.
Microorganisms can mediate in heavy metal sequestration through several cellular strategies and pathways. This offers an efficient way to remediate heavy metal polluted environments. This paper describes the ability of Escherichia coli K-12 to capture chromium(III) (Cr(III)) and the ultrastructural effects of this metal on cells, as well as the cellular metal localization and the possible sequestration strategy uses for it. The study was mainly performed by using several electron microscopy techniques and is based on the chromium trivalent concentration and the related exposure time. Transmission electron microscopy (TEM) assay was performed along with field emission scanning electron microscopy (FESEM) for morphological responses. Furthermore, TEM was coupled with an energy dispersive X-ray (TEM-EDX) and TEM with selected area electron diffraction (TEM-SAED) to conduct analytical assays. The exposed cultures to 10 and 12 mM Cr(III) at 12 h and to 5, 7, 10, 12, 13, and 15 mM of Cr(III) at 24 h indicated the presence of multiple electrodense granules that were significantly enriched in chromium and phosphorus content via EDX analysis. Moreover, these granules were observed to be attached to external membrane and/or surrounding cells in the respective ultrathin sections analyzed under TEM. According to these results, E. coli K-12 possesses the ability to immobilize Cr(III) in external polyphosphate granules through a strategy of accumulation, where cell response to Cr(III) toxicity seems to have a dose-dependent and time-dependent relation, thereby offering significant potential for bioremediation in Cr(III)-contaminated areas.
微生物可以通过多种细胞策略和途径来介导重金属的固定。这为修复重金属污染环境提供了一种有效的方法。本文描述了大肠杆菌 K-12 捕获铬(III) (Cr(III))的能力，以及这种金属对细胞的超微结构影响，以及细胞内金属的定位和可能的固定策略。这项研究主要通过使用几种电子显微镜技术来完成，其基础是三价铬的浓度和相关的暴露时间。透射电子显微镜（TEM）分析与场发射扫描电子显微镜（FESEM）一起进行形态学反应。此外，TEM 与能量色散 X 射线（TEM-EDX）和 TEM 与选区电子衍射（TEM-SAED）相结合进行分析测试。在 12 小时内将暴露于 10 和 12 mM Cr(III)的培养物和在 24 小时内暴露于 5、7、10、12、13 和 15 mM Cr(III)的培养物的结果表明，存在多种电密颗粒，这些颗粒通过 EDX 分析显示出对铬和磷含量的显著富集。此外，在 TEM 下分析相应的超薄切片时，观察到这些颗粒附着在外膜和/或周围细胞上。根据这些结果，大肠杆菌 K-12 具有通过积累策略将 Cr(III)固定在外部多磷酸盐颗粒中的能力，其中细胞对 Cr(III)毒性的反应似乎具有剂量和时间依赖性关系，从而为 Cr(III)污染地区的生物修复提供了重要的潜力。
