A novel, anaerobically grown microbial biofilm, scraped from the inner surface of a borehole, 1474 m below land surface within a South African, Witwatersrand gold mine, contains framboidal pyrite. Water flowing from the borehole had a temperature of 30.9 degrees C, a pH of 7.4, and an Eh of -50 mV. Examination of the biofilm using X-ray diffraction, field emission gun scanning electron microscope equipped for energy dispersive X-ray microanalysis demonstrated that the framboids formed within a matrix of bacteria and biopolymers. Focused ion beam sectioning of framboids followed by NEXAFS measurements using both scanning transmission X-ray microscopy and X-ray photoelectron emission microscopy revealed that the pyrite crystals grew within an organic carbon matrix consisting of exopolysaccharides and possibly extracellular DNA, which is intuitively important in sulfide mineral diagenesis. Growth of individual pyrite crystals within the framboid occurred inside organic templates confirms the association between framboidal pyrite and organic materials in low-temperature diagenetic environments and the important role of microenvironments in biofilms in regulating geochemical cycles.

中文翻译：

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在低温细菌生物膜中形成的黄菊黄铁矿的高分辨率化学和结构研究。

一种新型的，厌氧生长的微生物生物膜，是从南非威特沃兹朗德金矿的地表以下1474 m的一个钻孔内表面刮下来的，其中含有黄铁矿黄铁矿。从钻孔流出的水的温度为30.9摄氏度，pH为7.4，Eh为-50 mV。使用X射线衍射，配备了能量色散X射线微分析的场发射枪扫描电子显微镜对生物膜进行检查，结果表明，在细菌和生物聚合物的基质中形成了黄烷类物质。聚焦离子束切片的果糖，然后使用扫描透射X射线显微镜和X射线光电子发射显微镜进行NEXAFS测量，发现黄铁矿晶体生长在由胞外多糖和可能的细胞外DNA组成的有机碳基质中，这在硫化物成岩作用中很重要。在有机模板内部发生的黄菊体内单个黄铁矿晶体的生长证实了低温成岩环境中黄菊黄铁矿与有机物质之间的关联，以及微环境在生物膜中调节地球化学循环的重要作用。