矿物及地球化学条件对矿物界面的微生物行为及土壤胞外酶稳定性影响研究

在岩石圈-生物圈相互作用过程中，人们通常认为，生物是界面反应的主要驱动因子，而矿物及岩石只是被动接受改造的对象。因此，目前大部分研究忽略了生物与周围地质环境之间的耦合及生物反馈，从而导致对岩石圈-生物圈相互作用的认识存在不足。本项目的总体目标是研究矿物及地球化学条件对微生物行为及土壤胞外酶活性及稳定性的调控过程与机制。本项目拟通过野外及实验室内工作从三个方面对上述研究目标进行阐释：第一，研究微生物与营养及能量缺乏型矿物相互作用的动机与机理；第二，研究微生物对矿物及地球化学条件变化的响应规律及分子调控机制；第三，研究矿物提高胞外酶稳定性的机制。为此，我们提出科学假设：（1）微生物与矿物进行相互作用是为了应对环境胁迫而对其生境（矿物）进行修饰的过程；（2）球状胞外酶的表面生物成矿对酶的保护起重要作用。预计研究成果可为矿物的生物风化过程及土壤碳循环研究提供新的理论基础。

Conventional approach to geosphere-biosphere interaction (one of the critical processes shaping Earth-surface environment) treats geomaterial (rocks and minerals) as passive objects while organisms operative forces actively engaged in reactions at the bio-geo interfaces. As such, from a systems-approach point of view, majority of existing studies ignored the coupling and feedback relations between bio-activities and the hosting environment, leading to a gap in our understanding of geo-bio interactions. The overarching goal of this project is to examine how mineralogical and geochemical conditions govern (1) the behavior of inhabiting microorganisms and (2) the activity/stability of extracellular bioproducts in soil environments. To fulfill the objective, we plan to investigate three specific questions through laboratory and field work:1. Why do microbes interact with minerals having no nutritional and energy values? 2. How do microbes respond to changes in geochemical conditions? 3. How do minerals stabilize soil exoenzymes without living microbes? We hypothesize that (1) microbial interactions with minerals (e.g. feldspars, quartz, kaolinite) that do not benefit cellular growth and respiration is driven by organisms’ need to reduce environmental stress. Consequently, the cell-mineral interactions are guided by specific environmental conditions to eliminate the stress factors such as toxic metals and radicals; (2) soil exoenzymes are stabilized and preserved by a biomineralized coating of poorly- to non-crystalline Fe and Al (hydr)oxides formed at the protein globules’ exterior through molecular recognition at the organic-mineral interfaces. We believe the acquired results can significantly expand our current knowledge base in biogeochemical weathering and pedospheric C cycle.