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。在大多数城市污水处理厂中，使用生物过程，活性污泥（AS），通过将好氧硝化过程（其将铵氧化成硝酸盐）与厌氧反硝化过程（其将硝酸盐还原成良性二氮气体（N2））耦合来去除氮。然而，AS反应器中的铵硝化需要使用曝气来供应氧气，这需要大量的能量并且占WWTP中使用的总能量的70- 80%。厌氧氨氧化法是一种具有较低能耗和运行成本的城市污水脱氮工艺。然而，厌氧氨氧化细菌的选择，培养和整合到反应器和城市污水处理厂的处理列车仍然是一个挑战，由于其缓慢的生长速率和竞争，从其他微生物，包括铵氧化细菌（AOB）和亚硝酸盐氧化细菌（NOB）。最近的研究表明，厌氧氨氧化微生物可以发电。基于这些有前途的研究，该项目的主要研究人员（PI）建议使用生物电化学系统探索电活性厌氧氨氧化细菌的选择，以加速其在城市污水中的生长，增殖和稳定性。 该项目的成功完成将通过产生环境微生物学和生物技术的基础知识，促进开发和部署更具成本效益的城市和工业废水脱氮解决方案，造福社会。通过学生教育和培训，包括指导坦普尔大学的一名研究生和马里兰州大学的一名研究生，将为社会带来额外的好处。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），但对anammox细菌通过细胞外将电子转移到电极的机制知之甚少，而对于电子如何在细胞内从脱氨酶体转运到下游EET的外膜蛋白质，则知之甚少。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物群落的微生物生态学和生态生理学的基本理解。拟议研究的核心和指导假设是，在BES中，EET依赖的厌氧氨氧化是由电活性厌氧氨氧化细菌及其电活性伙伴组成的微生物种群进行的。它们一起形成了一种互利关系：厌氧氨氧化细菌固定二氧化碳并为电活性细菌提供有机物质，电活性细菌的电子穿梭被厌氧氨氧化细菌清除用于EET。如果假设成立，EET依赖的厌氧氨氧化可以通过电化学增强这两个合作伙伴的富集。本研究的具体目标是：1）开发电化学策略以构建电活性厌氧氨氧化群落; 2）了解电活性厌氧氨氧化群落中的微生物相互作用; 3）阐明EET依赖的厌氧氨氧化代谢途径。该项目的成功完成具有潜在的变革性影响，通过产生新的基础知识的微生物生态学和生态生理学的电活性厌氧氨氧化微生物在BES指导设计和实施更可持续的 从城市和工业废水中去除氮的技术和解决方案。为了实现该项目的教育和培训目标，PI建议利用坦普尔大学（TU）和马里兰州大学（UMD）的现有项目，从代表性不足的群体中招募和指导本科生从事该项目。此外，PI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/本科课程中。该奖项反映了NSF的法定使命，并被认为值得通过使用基金会的知识价值和更广泛的影响审查标准进行评估来支持。

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.