Sustainable bioproduction using phototrophic extracellular electron uptake

一些细菌能够利用来自光的电力和能量来固定二氧化碳，最终用于可再生的、碳中性的、到封存碳的某些高价值化合物的生产。该项目的总体目标是更好地了解这一生物生产过程，并设计细菌将这一过程用于生物塑料和生物燃料生产。该项目将为高中、本科生和研究生创造身临其境的研究机会。微生物还原-氧化反应推动生物圈内的物质和能量流动。大多数微生物使用可溶性电子供体和受体，但也有一些使用固相导电物质。潜在的微生物过程被称为细胞外电子转移(EET)。在EET过程中，电子流动的方向性可以是向外的，其中固相导电物质通过还原EET被微生物还原；或者向内，其中固相导电物质通过细胞外电子摄取(EEU)被氧化。虽然还原EET的研究由来已久，但EEU最近才崭露头角，并代表了微生物生物地球化学的范式转变。这是因为具有EEU能力的微生物可以氧化丰富的固相导电物质，如用于微生物生长的矿物质。许多微生物可以执行EEU，但只有这些微生物中的一部分可以执行光养EEU。这种特殊的新陈代谢利用固体导电矿物或其替代品(固定电极)中的光和电子的能量来固定二氧化碳。因此，光营养-EEU代表了一种新的代谢工程，以实现可持续的、碳中性到固碳的生物生产。为了了解光营养EEU在环境中的流行情况，并充分发挥其生物工程潜力，必须解决几个基本的知识空白。其中包括对电子输入模块及其调节的深入描述；以及电子转移路径和细胞电子汇。利用多组学和跨学科的方法，该项目旨在填补这些知识空白，以获得对淡水微生物沼泽红假单胞菌和海洋微生物硫磺嗜酸红假单胞菌中光营养EEU的系统水平的了解。该项目将利用合成生物学、代谢工程和材料科学，利用光养EEU提高生物塑料和生物燃料的可持续生产。总之，该项目将扩大我们对光营养EEU的理解，并探索利用具有光营养EEU能力的微生物沼泽红假单胞菌生产可持续的生物制品。该项目还将吸引来自不同教育水平的学生参与可持续发展研究。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Some bacteria are capable of using electricity and energy from light to fix carbon dioxide and ultimately for renewable, carbon-neutral to carbon-sequestering production of certain high value compounds. The overall goal of this project is to better understand this bioproduction process and to engineer bacteria to use this process for bioplastic and biofuel production. This project will create immersive research opportunities for students at the high school, undergraduate and graduate school levels. Microbial reduction-oxidation reactions drive matter and energy flow in the biosphere. Most microbes use soluble electron donors and acceptors, but some use solid-phase conductive substances. The underlying microbial process is called extracellular electron transfer (EET). The directionality of electron flow during EET can be either outbound, where solid-phase conductive substances are microbially reduced via reductive-EET; or inbound, where solid-phase conductive substances are oxidized via extracellular electron uptake (EEU). While reductive-EET is long studied, EEU has come to fore recently, and represents a paradigm shift in microbial biogeochemistry. This is because EEU-capable microbes can oxidize abundant solid-phase conductive substances such as minerals for microbial growth. A number of microbes can perform EEU, but only a subset of these organisms can perform phototrophic-EEU. This specialized metabolism harnesses the energy of light and electrons from solid-conductive minerals or their proxies (poised electrodes) to fix carbon dioxide. Accordingly, phototrophic-EEU represents a new metabolism to engineer for sustainable, carbon-neutral to carbon-sequestering bioproduction. To understand the environmental prevalence of phototrophic-EEU, and realize its full bioengineering potential, several fundamental knowledge gaps must be addressed. These include in-depth characterization of the electron input modules and their regulation; and the electron transfer pathways and the cellular electron sinks. Using multi-omic and transdisciplinary approaches, this project aims to fill these knowledge gaps to gain a systems-level understanding of phototrophic-EEU in the freshwater microbe, Rhodopseudomonas palustris and the marine microbe Rhodovulum sulfidophilum. The project will use synthetic biology, metabolic engineering, and material science to improve sustainable production of bioplastics and biofuels using phototrophic-EEU. Together, this project will expand our understanding of phototrophic-EEU, and explore the production of sustainable bioproducts using the phototrophic-EEU capable microbe, Rhodopseudomonas palustris. This project will also engage students from various educational levels in sustainability research.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.