Unraveling the evolutionary, ecological and structural basis of microbial fiber degradation in nature

自从陆地上有生命以来，地球的陆地食物链一直是基于微生物对光合作用产物中纤维素纤维的降解。虽然已有大量研究致力于陆地植物产生纤维的光合作用过程的进化起源和机制，但对微生物纤维分解的进化和生态学知之甚少。在这里，我们建议结合前沿的研究工具和专业知识，通过应用微生物生态学、细胞外蛋白质组学、纤维降解酶学、结构生物学和分子进化，在纳米尺度上了解纤维降解的进化史及其与微生物生态学的相互联系。为此，在我们的第一个目标中，我们将破译陆地纤维降解的进化起源及其在自然界中的发生。这些信息将有助于我们的第二个目标，以揭示建立在自然界中微生物纤维降解的酶学和生态学的指导原则。最后，在我们的第三个目标中，我们将通过冷冻电子断层扫描(CRYO-ET)的空间和结构高分辨率分析，在纳米尺度上了解微生物纤维降解的生态和进化。实现这些目标将使我们能够从生化、结构和生理的角度，对微生物纤维降解的生态学和进化如何相互交织和反映在单个微生物和群落的背景下获得答案和深刻的见解。因此，我们的研究将为定义和更好地理解纤维降解在自然界中的核心作用提供踏脚石，并将揭示天然纤维降解微生物生态系统的地球历史。

For as long as there has been life on land, Earth's terrestrial food chain has been based on the microbial degradation of cellulose-based fiber of photosynthetic products. Although extensive research has been dedicated to the evolutionary origins and mechanisms of the photosynthetic processes of land plants that generate fiber, very little is known about the evolution and ecology ofmicrobial fiber breakdown. Here, we propose a focused effort uniting cutting-edge research tools and expertise, by applying microbial ecology, extracellular proteomics, fiber-degrading enzymology, structural biology and molecular evolution, to understand the evolutionary history of fiber degradation and its interconnectivity with microbial ecology at a nanoscale resolution. To this end, in our first aim we will decipher the evolutionary origin of terrestrial fiber degradation and its occurrence in nature. This information will facilitate our second aim to uncover guiding principles for the establishment of enzymology and ecology of microbial fiber degradation in nature. Finally, in our third aim we will understand the ecology and evolution of microbial fiber degradation at the nanoscale resolution through spatial and structural high-resolution analysis via cryo-electron tomography (cryo-ET). Meeting these aims will enable us to gain answers and deep insights into how ecology and evolution of microbial fiber degradation are intertwined and reflected at the single-microbe and community context, from the biochemical, structural and physiological perspectives. Our study will thus provide astepping-stone towards defining and better understanding the central role of fiber degradation in nature and will reveal the Earth history of natural fiber-degrading microbial ecosystems.