IMPMC, Sorbonne Université, MNHN, UPMC, CNRS UMR 7590, 4 pl. Jussieu, 75005, Paris, France.
MCAM, MNHN, UPMC, CNRS UMR 7245, 63 rue Buffon, 75005, Paris, France.
Sci Rep. 2017 Dec 5;7(1):16984. doi: 10.1038/s41598-017-17111-9.
Burial is generally detrimental to the preservation of biological signals. It has often been assumed that (bio)mineral-encrusted microorganisms are more resistant to burial-induced degradation than non-encrusted ones over geological timescales. For the present study, we submitted Sulfolobus acidocaldarius experimentally encrusted by amorphous Fe phosphates to constrained temperature conditions (150 °C) under pressure for 1 to 5 days, thereby simulating burial-induced processes. We document the molecular and mineralogical evolution of these assemblages down to the sub-micrometer scale using X-ray diffraction, scanning and transmission electron microscopies and synchrotron-based X-ray absorption near edge structure spectroscopy at the carbon K-edge. The present results demonstrate that the presence of Fe-phosphates enhances the chemical degradation of microbial organic matter. While Fe-phosphates remained amorphous in abiotic controls, crystalline lipscombite (FeFe(PO)(OH)) entrapping organic matter formed in the presence of S. acidocaldarius cells. Lipscombite textures (framboidal vs. bipyramidal) appeared only controlled by the initial level of encrustation of the cells, suggesting that the initial organic matter to mineral ratio influences the competition between nucleation and crystal growth. Altogether these results highlight the important interplay between minerals and organic matter during fossilization, which should be taken into account when interpreting the fossil record.
埋葬通常不利于生物信号的保存。人们通常认为，在地质时间尺度上，与未包裹的微生物相比，（生物）矿物包裹的微生物对埋葬诱导的降解更具抵抗力。在本研究中，我们将实验包裹在无定形磷酸铁中的 Sulfolobus acidocaldarius 置于受限制的温度条件（150°C）下，在压力下处理 1 至 5 天，从而模拟埋葬诱导的过程。我们使用 X 射线衍射、扫描和透射电子显微镜以及基于同步加速器的碳 K 边 X 射线吸收近边结构光谱，在亚微米尺度上记录了这些组合的分子和矿物演化。目前的结果表明，磷酸铁的存在增强了微生物有机质的化学降解。虽然在非生物对照中磷酸铁仍保持无定形，但在存在 S. acidocaldarius 细胞的情况下形成了包裹有机质的结晶 lipscombite（FeFe(PO)(OH)）。lipscombite 结构（鲕状 vs. 双锥）仅受细胞最初包裹水平的控制，表明初始有机质与矿物的比例影响成核和晶体生长之间的竞争。总之，这些结果强调了在化石形成过程中矿物质和有机质之间的重要相互作用，在解释化石记录时应考虑到这一点。
