Collaborative Research: Shedding Light on The Microbial Ecologyand Ecophysiology of Electroactive Anammox Communities

污水处理厂在环境保护中起着至关重要的作用。在美国，市政污水处理厂每天处理数十亿加仑的废水，以去除悬浮固体、有机物和过量的氮营养物质，如铵。在大多数市政污水处理厂中，生物工艺--活性污泥(AS)--通过将氨氧化为硝酸盐的好氧硝化过程和随后将硝酸盐还原为良性氮氮气体(N_2)的厌氧反硝化过程相耦合来去除氮。然而，AS反应器中的氨硝化需要曝气供氧，这需要大量的能量，占污水处理厂总能量的70%-80%。厌氧氨氧化(Anammox)是一种具有较低能耗和运行成本的去除城市污水中氮的微生物工艺。然而，由于厌氧氨氧化细菌的生长速度慢，以及来自氨氧化细菌(AOB)和亚硝酸盐氧化细菌(NOB)等其他微生物的竞争，厌氧氨氧化细菌的选择、培养和整合到城市污水处理厂的反应器和处理系统中仍然是一个挑战。最近的研究表明，厌氧氨氧化微生物可以发电。在这些有希望的研究的基础上，该项目的首席研究员(PI)建议探索利用生物电化学系统选择具有电活性的厌氧氨氧化细菌，以加速它们在城市污水中的生长、增殖和稳定性。这一项目的成功完成将使社会受益，因为它将产生环境微生物学和生物技术方面的基本知识，以推动开发和部署更具成本效益的市政和工业废水脱氮解决方案。通过学生教育和培训将实现更多的社会利益，包括对坦普尔大学和马里兰大学的一名研究生和一名研究生的指导。厌氧氨氧化(Anammox)细菌最近被证明可以进行细胞外电子转移(EET)，但人们对厌氧氨氧化细菌将电子从细胞外转移到电极的机制知之甚少，更不知道电子是如何从厌氧氨氧化细菌的细胞内传输到EET下游的外膜蛋白的。该项目的总体目标是促进对生物电化学系统(BES)中电活性厌氧氨氧化群落的微生物生态学和生态生理学的基本了解。这项研究的核心和指导性假设是，在BES中，依赖EET的厌氨氧化是由电活性厌氨氧化细菌及其电活性伙伴组成的微生物种群进行的。它们共同形成了一种互惠互利的关系：厌氧氨氧化细菌固定二氧化碳，并向电活性细菌提供有机物，而电活性细菌的电子穿梭被厌氧氨氧化细菌清除以获得EET。如果假设成立，EET依赖的Anammox可以通过这两个伙伴的富集化而得到电化学增强。研究的具体目的是：1)开发建立电活性厌氧氨氧化群落的电化学策略；2)了解电活性厌氧氨氧化群落中微生物的相互作用；3)阐明EET依赖的厌氨氧化菌的代谢途径。该项目的成功完成有可能产生变革性的影响，通过产生有关BES电活性厌氨氧化微生物群的微生物生态学和生态生理学的新基础知识，指导设计和实施更可持续的技术和解决方案，以从市政和工业废水中去除氮。为了落实该项目的教育和培训目标，私人投资机构建议利用坦普尔大学(TU)和马里兰大学(UMD)的现有项目，从代表性不足的群体中招募和指导本科生参与该项目。此外，PIS计划将这项研究的结果整合到TU和UMD现有的环境工程研究生/本科生课程中。这一奖项反映了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。

Wastewater treatment plants (WWTPs) play a critical role in environmental protection. In the United States, municipal WWTPs process billions of gallons of wastewater every day to remove suspended solids, organic matter, and excess nitrogen nutrients such as ammonium. In most municipal WWTPs, a biological process, activated sludge (AS), is used to remove nitrogen by coupling an aerobic nitrification process which oxidizes ammonium into nitrate followed by an anaerobic denitrification process that reduces the nitrate to benign dinitrogen gas (N2). However, ammonium nitrification in AS reactors requires the supply of oxygen using aeration which requires a significant amount of energy and accounts for 70-80 % of the total energy used in WWTPs. Anaerobic ammonium oxidation (anammox) has emerged as a promising microbial process for removing nitrogen from municipal wastewater with lower energy consumption and operating costs. However, the selection, cultivation, and integration of anammox bacteria into reactors and the treatment trains of municipal WWTPs has remained a challenge due to their slow growth rates and competition from other microorganisms including ammonium oxidizing bacteria (AOB) and nitrite oxidizing bacteria (NOB). Recent studies show that anammox microbes can generate electricity. Building upon these promising studies, the Principal Investigators (PIs) of this project propose to explore the selection of electroactive anammox bacteria using bioelectrochemical systems with the goal of accelerating their growth, proliferation, and stability in municipal wastewater. The successful completion of this project will benefit society through the generation of fundamental knowledge in environmental microbiology and biotechnology to advance the development and deployment of more cost-effective solutions for nitrogen removal from municipal and industrial wastewater. Additional benefits to society will be achieved through student education and training including the mentoring of one graduate student at Temple University and one graduate student at the University of Maryland.Anaerobic ammonium oxidation (anammox) bacteria have recently been shown to perform extracellular electron transfer (EET), but little is known about the mechanisms through which anammox bacteria transfer electrons extracellularly to electrodes, and even less is known about how electrons are transported intracellularly from the anammoxosome to the outer membrane proteins for downstream EET. The overarching goal of this project is to advance the fundamental understanding of the microbial ecology and ecophysiology of electroactive anammox communities in bioelectrochemical systems (BES). The core and guiding hypothesis of the proposed research is that in BES, EET-dependent anammox is carried out by a microbial population composed of electroactive anammox bacteria and their electroactive partners. Together they form a mutualistic relationship: anammox bacteria fix carbon dioxide and provide organic matter to electroactive bacteria, whose electron shuttles are scavenged by anammox bacteria for EET. If the hypothesis holds, EET-dependent anammox could be electrochemically enhanced through the enrichment of those two partners. The specific aims of the research are to 1) develop electrochemical strategies to build electroactive anammox communities; 2) understand the microbial interactions in electroactive anammox communities; and 3) elucidate the metabolic pathways involved in EET-dependent anammox. The successful completion of this project has the potential for transformative impact through the generation of new fundamental knowledge on the microbial ecology and ecophysiology of electroactive anammox microbiomes in BES to guide the design and implementation of more sustainable technologies and solutions to remove nitrogen from municipal and industrial wastewater. To implement the education and training goals of the project, the PIs propose to leverage existing programs at Temple University (TU) and the University of Maryland (UMD) to recruit and mentor undergraduate students from underrepresented groups to work on the project. In addition, the PIs plan to integrate the findings from this research into existing environmental engineering graduate/undergraduate courses at TU and UMD.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.