Quantitative mapping of toxic metals on the submicron-scale in cell-mineral aggregates formed by iron mineral precipitating and dissolving bacteria

Cr、Co、Ni、Cu、Zn、as、Cd、Hg和Pb等有毒微量金属在自然环境和污染环境中的分布、迁移和生物利用度往往受有机生物大分子吸附和（生物）矿物（特别是铁矿物）吸附和共沉淀的控制。具有陡峭地球化学梯度的化学微环境和亚微环境控制着相关相的形态形成和稳定性。基于同步辐射的扫描透射x射线显微镜（STXM）将结合近边缘x射线吸收精细结构（NEXAFS）的物种形成灵敏度与≤30 nm的空间分辨率，在水合、接近自然的环境中，研究复杂环境生物膜-矿物聚集体的亚微米尺寸异质性和化学微生态位对有毒微量金属物种形成和分配的影响。2D和3d层析STXM将被优化，以允许对主要有机大分子和相关金属和矿物的形态进行原位分析。在化学控制良好的条件下，将研究Ni， Cu和Zn在分析良好的细菌模型菌株，它们的外聚合物和相关的铁生物矿物之间的形态和分配。最后，金属物种形成和划分将在原始和人为影响的环境系统中进行量化和绘制。结合使用特定荧光染料和探针的共聚焦激光扫描显微镜将用于扩大STXM结果并进一步表征外聚合物。

The distribution, mobility and bioavailability of toxic trace metals such as Cr, Co, Ni, Cu, Zn, As, Cd, Hg, and Pb in natural and contaminated environments are often controlled by the sorption to organic biomacromolecules and by the sorption to and co-precipitation with (bio-)minerals, in particular Fe-minerals. Chemical micro- and submicro-environments with steep geochemical gradients control speciation and stability of the involved phases. The influence of the submicron-size heterogeneity and chemical micro-niches of complex environmental biofilm-mineral aggregates on the speciation and partitioning of toxic trace metals will be studied in hydrated, close-to-natural environments at the spatially relevant scale using synchrotron-based scanning transmission X-ray microscopy (STXM) which combines near edge X-ray absorption fine structure (NEXAFS) based speciation sensitivity with ≤ 30 nm spatial resolution. 2D and 3D-tomographic STXM will be optimized to allow for the in-situ analysis of the speciation of major organic macromolecules and the associated metals and minerals. The speciation and partitioning of Ni, Cu and Zn between well-analyzed bacterial model strains, their exopolymers and associated Fe-biominerals will be studied under chemically well controlled conditions. Finally, metal speciation and partitioning will be quantified and mapped in both pristine and anthropogenically influenced environmental systems. The combination with confocal laser scanning microscopy using specific fluorescence dyes and probes will be used for up-scaling the STXM results and further characterizing the exopolymers.