STXM and NanoSIMS investigations on EPS fractions before and after adsorption to goethite.
STXM and NanoSIMS investigations on EPS fractions before and after adsorption to goethite.
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DOI：
10.1021/es3039505
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发表时间：
2013-03
影响因子：
11.4
通讯作者：
Xinran Liu;K. Eusterhues;J. Thieme;V. Ciobotă;C. Höschen;C. Mueller;K. Küsel;I. Kögel‐Knabner
中科院分区：
文献类型：
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作者：
Xinran Liu;K. Eusterhues;J. Thieme;V. Ciobotă;C. Höschen;C. Mueller;K. Küsel;I. Kögel‐Knabner
胞外聚合物（EPS）是土壤中无机-有机结合体形成的重要来源。因为这样的形成会影响移动的和非移动的有机物的组成以及矿物的反应性，我们研究了EPS的组成之前和之后吸附针铁矿。拉曼测量从枯草芽孢杆菌提取的EPS区分四个级分富含蛋白质，多糖，脂质，或脂质和蛋白质。扫描透射X-射线显微镜确定了三种不同的EPS组分，其组成不同的蛋白质，非芳香族蛋白质和多糖。EPS与针铁矿反应导致脂质和蛋白质的优先吸附。有机覆盖是不均匀的，由约100 × 200 nm的富含脂质或富含蛋白质的大斑块组成。纳米二次离子质谱显示，在针铁矿吸附的EPS中，~400 nm的聚集体中存在强烈的S富集。从我们的简化模型系统中，我们了解到只有一小部分（<10%）的EPS通过吸附固定到针铁矿。该部分形成了间隔亚μm的富含蛋白质和富含脂质的区域的涂层，即，这两种材料的反应位点有很大的不同。这将最终影响进一步的吸附，颗粒的流动性，并最终也胶体的稳定性。
Extracellular polymeric substances (EPS) are expected to be an important source for the formation of mineral-organic associations in soil. Because such formations affect the composition of mobile and immobile organic matter as well as the reactivity of minerals, we investigated the composition of EPS before and after adsorption to goethite. Raman measurements on EPS extracted from Bacillus subtilis distinguished four fractions rich in proteins, polysaccharides, lipids, or lipids and proteins. Scanning transmission X-ray microscopy identified three different EPS-fractions that varied in their composition in proteins, nonaromatic proteins, and polysaccharides. Reaction of EPS with goethite led to a preferential adsorption of lipids and proteins. The organic coverage was heterogeneous, consisting of ~100 × 200 nm large patches of either lipid-rich or protein-rich material. Nanoscale secondary ion mass spectrometry showed a strong S enrichment in aggregates of ~400 nm in the goethite adsorbed EPS. From our simplified model system, we learned that only a small portion (<10%) of EPS was immobilized via adsorption to goethite. This fraction formed a coating of subμm spaced protein-rich and lipid-rich domains, i.e., of two materials which will strongly differ in their reactive sites. This will finally affect further adsorption, the particle mobility and eventually also colloidal stability.