Beyond the Monod Equation: Developing a New Theory of Geomicrobial Kinetics

智力优势：本提案的主要目标是为地质环境中微生物代谢动力学发展一种新的速率定律。新的速率定律将通过计算可利用能量和微生物多样性如何控制地质环境中微生物代谢的进展来推进地球生物学和生物地球化学的研究。研究者将在以下基础上发展新的速率定律：(1)微生物代谢热力学控制的理论模型；(2)碰撞理论对微生物动力学参数的限制和微生物生长的最低要求；(3)环境中微生物分类类群的多样性和丰度。新速率定律的这三个基础导致了三个主要的研究任务：(1)量化地质环境中热力学控制对微生物代谢的意义；(2)建立将微生物多样性纳入动力学速率规律的理论方法；(3)通过将两种模型的输出值与原位产甲烷速率作为测试案例，将新模型与传统动力学模型（即Monod方程）的性能进行比较。他们将开发新的速率定律，并将其应用于预测俄勒冈州中南部上克拉马斯湖沉积物中甲烷生成的季节性速率。他们的初步结果表明，甲烷菌多样性适中，但产甲烷率显著。这些沉积物中有机质负荷的季节性变化导致了电子供体浓度的大范围变化，为我们发展新的地球微生物动力学理论提供了一个自然实验。本提案中提出的新速率定律考虑了环境中生物地球化学过程的两个关键但在很大程度上被忽视的控制因素，即化学能的可用性和微生物的多样性。因此，新的速率定律弥补了适用于能量丰富条件下纯培养物的经验速率定律（如莫诺方程）与地质环境中各种微生物动力学之间的差距。新理论将地球化学和微生物多样性整合到地球微生物动力学中，因此，推动了正在进行的研究工作，旨在了解地质环境作为多种微生物的栖息地。新理论可以应用于自然环境和污染地区的微生物活动预测，或者在无法直接采样的偏远地区。更广泛的影响：拟议的研究解决了地球生物学和生物地球化学中一个引人注目的问题&amp；#8722；如何预测地质环境中各种微生物的活动？研究人员将使用我们的多学科方法提供从K-12到研究生的各个层次的学习机会。他们将与现场附近一所高中的科学教师合作，开发一个可持续的、可复制的关于甲烷生成动力学和碳循环的课堂单元。本单元将以探究为基础，通过一系列以共同主题为中心的实地实践和实验室体验，向学生介绍环境科学。俄勒冈州湖泊的碳循环。该单元将分发给俄勒冈州所有的K-12教育工作者，它的设计将满足俄勒冈州教育委员会对俄勒冈州公立学校额外的探究式科学教学的新要求。拟建项目将资助两名博士生。pi还将通过美国国家科学基金会资助的本科生催化推广和研究经验项目和俄勒冈大学本科生研究暑期项目的支持，招募三到四名本科生加入我们的研究项目。

Intellectual Merit: The primary objective of this proposal is to develop a new rate law for the kinetics of microbial metabolisms in geological environments. The new rate law will advance the study of geobiology and biogeochemistry by accounting for how available energy and microbial diversity control the progress of microbial metabolisms in geological environments. Investigators will develop the new rate law based on: (1) a theoretical model for thermodynamic control of microbial metabolisms; (2) limits to microbial kinetic parameters derived from collision theory and the minimum requirements for microbial growth; and (3) the diversity and abundance of microbial taxonomic groups in the environment. These three bases of the new rate law lead to three primary research tasks: (1) quantifying the significance of thermodynamic control on microbial metabolisms in geological environments; (2) developing a theoretical approach that integrates microbial diversity into kinetic rate laws; and (3) comparing the performance of the new model to traditional kinetic models (i.e., the Monod equation) by comparing the output of both models to in situ rates of methanogenesis as a test case. They will develop the new rate law and apply it to predicting the seasonal rates of methanogenesis in the sediments of Upper Klamath Lake in southcentral Oregon. Their preliminary results demonstrate modest methanogen diversity but significant rates of methanogenesis. Seasonal variation in organic matter loading into these sediments leads to a wide range in electron donor concentrations, offering a natural experiment for developing our new theory of geomicrobial kinetics. The new rate law developed in this proposal accounts for two critical, yet largely neglected, controlling factors on biogeochemical processes in the environment, i.e., the availability of chemical energy and the diversity of microorganisms. The new rate law therefore bridges the gap between empirical rate laws (e.g., the Monod equation) applicable for pure-cultures under energy-rich conditions and the kinetics of diverse microorganisms in geological environments. The new theory integrates geochemistry and microbial diversity into geomicrobial kinetics and, therefore, advances ongoing research efforts that seek to understand geological environments as habitats for diverse microorganisms. The new theory can be applied to the prediction of microbial activities in both natural environments and polluted areas, or in remote sites where direct sampling is not feasible. Broader Impacts: The proposed research addresses a compelling question in geobiology and biogeochemistry − how to predict the activities of diverse microorganisms in geological environments? Investigators will use our multidisciplinary approach to provide learning opportunities at all levels from K-12 to postgraduate. They will collaborate with science instructors at a high school near the field site to develop a sustainable and replicable classroom unit on the kinetics of methanogenesis and the carbon cycle. This unit will be inquiry-based and will introduce students to environmental science via a series of hands-on field and laboratory experiences centered on a common theme ? the cycling of carbon in Oregon lakes. The unit will be distributed to all Oregon K-12 educators, and it will be designed to meet a new requirement of the Oregon State Board of Education for additional inquiry-based science instruction in Oregon public schools. The proposed project will support two Ph.D. students. PIs will also recruit three to four undergraduate students into our research program via the support of the NSF-funded Undergraduate Catalytic Outreach and Research Experiences program and the Summer Program for Undergraduate Research at the University of Oregon.