Accurate mapping of the composition and structure of minerals and associated biological materials is critical in geomicrobiology and environmental research. Here, we have developed an apparatus that allows the correlation of cryogenic transmission electron microscopy (cryo-TEM) and synchrotron hard X-ray microprobe (SHXM) data sets to precisely determine the distribution, valence state, and structure of selenium in biofilms sampled from a contaminated aquifer near Rifle, CO. Results were replicated in the laboratory via anaerobic selenate-reducing enrichment cultures. 16S rRNA analyses of field-derived biofilm indicated the dominance of Betaproteobacteria from the Comamonadaceae family and uncultivated members of the Simplicispira genus. The major product in field and culture-derived biofilms is ∼25–300 nm red amorphous Se⁰ aggregates of colloidal nanoparticles. Correlative analyses of the cultures provided direct evidence for the microbial dissimilatory reduction of Se(VI) to Se(IV) to Se⁰. Extended X-ray absorption fine-structure spectroscopy showed red amorphous Se⁰ with a first shell Se–Se interatomic distance of 2.339 ± 0.003 Å. Complementary scanning transmission X-ray microscopy revealed that these aggregates are strongly associated with a protein-rich biofilm matrix. These findings have important implications for predicting the stability and mobility of Se bioremediation products and understanding of Se biogeochemical cycling. The approach, involving the correlation of cryo-SHXM and cryo-TEM data sets from the same specimen area, is broadly applicable to biological and environmental samples.

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相关低温光谱法研究硒生物还原产物

矿物和相关生物材料的成分和结构的准确绘图对于地球微生物学和环境研究至关重要。在这里，我们开发了一种装置，该装置可以将低温透射电子显微镜（cryo-TEM）和同步加速器硬X射线微探针（SHXM）数据集进行关联，以精确确定从生物膜中取样的生物膜中硒的分布，价态和结构。实验室附近的一处被污染的含水层。结果通过厌氧硒酸盐还原富集培养在实验室中重复进行。野外生物膜的16S rRNA分析表明，来自Comamonadaceae家族和未经培养的Simplicispira成员的β变形杆菌占主导地位。属。田间和培养衍生的生物膜的主要产物是约25–300 nm的胶态纳米颗粒红色无定形Se ⁰聚集体。文化的相关分析为微生物异化还原Se（VI）到Se（IV）到Se ⁰提供了直接的证据。扩展的X射线吸收精细结构光谱显示红色无定形Se ⁰第一壳Se–Se原子间距离为2.339±0.003Å。互补扫描透射X射线显微镜显示，这些聚集体与富含蛋白质的生物膜基质紧密相关。这些发现对预测硒生物修复产品的稳定性和迁移性以及对硒生物地球化学循环的理解具有重要意义。该方法涉及来自同一标本区域的cryo-SHXM和cryo-TEM数据集的相关性，广泛适用于生物和环境样品。