Preservation of bacterial microfossils of Fe-oxidizing bacteria during diagenesis of sedimentary deposits, i.e. banded iron formations

前寒武纪沉积沉积物，如带状铁地层（BIFs）是研究人员关注的焦点，他们旨在了解早期生命及其与地球大气演化的相关性。铁氧化细菌被认为参与了前寒武纪bif的形成。该项目的主要目标是研究细胞-矿物聚集体的实验室尺度成岩过程，特别是在微米/亚微米尺度上识别和定量绘制指示细菌生命的结构和（有机）化学特征。为此目的，计划利用实验室培养的几种铁氧化细菌模型菌株的细胞矿物聚集体进行实验。细胞-矿物聚集体将暴露在系统地升高的温度和压力下，达到前寒武纪bif典型经历的条件。将确定一套合适的相关分析显微镜。样品将通过常规的超微切片和聚焦离子束（FIB）铣削制备，用于定性和定量分析电子和软x射线光谱显微镜研究，以研究细菌残留物的形态和（有机）化学指纹图谱。此外，残基的三维结构将被fib层析成像。红外光谱显微镜和共聚焦拉曼显微镜将在中等空间分辨率下提供进一步的化学信息。将比较三种不同类型的生物源铁矿物（包壳、非包壳和茎/鞘形成细菌）保存细菌微化石的潜力。

Precambrian sedimentary deposits such as banded iron formations (BIFs) are in the focus of researchers who aim to understand early life and its relevance for the evolution of the earth’s atmosphere. Iron-oxidizing bacteria are believed to be involved in the formation of Precambrian BIFs. The main goal of this project is to study on the laboratory scale diagenesis processes of cell-mineral aggregates and in particular to identify and quantitatively map structural and (organo-) chemical features on the micron- / submicronscale which are indicative of bacterial life. To this end experiments are planned with cellmineral aggregates of several model strains of laboratory cultures of Fe-oxidizing bacteria. Cell-mineral aggregates will be exposed to systematically increasing temperatures and pressures up to the conditions typically experienced by Precambrian BIFs. An appropriate set of correlative analytical microscopies will be determined. Samples will be prepared by conventional ultramicrotomy and focused-ion beam (FIB) milling for qualitative and quantitative analytical electron and soft X-ray spectromicroscopy studies to investigate both morphology and (organo-) chemical fingerprints of the bacterial residues. Additionally the 3D structure of the residues will be mapped by FIB-tomography. Infrared Spectromicroscopy and confocal Raman microscopy will provide further chemical information at moderate spatial resolution. The results from three different types of biogenic Fe-minerals (from encrusting, non-encrusting and stalk/sheath-forming bacteria) will be compared with regard to their potential for the preservation of bacterial microfossils.