Copper Nanoparticle Interactions with Nitrogen-Cycling Bacteria

1134355 Mahendra这个由纳米技术计划的环境健康和安全的NSF奖支持Shaily Mahendra教授的工作，以研究铜纳米颗粒（NPs）对自然和工程环境系统中参与氮循环的细菌的多样性和功能的影响。背景和意义 我们预计，在未来几十年内，含纳米材料的工程产品对废物流的投入将增加，将需要更多的工厂对废水进行三级处理。 环境中氮的转化是由微生物驱动的;硝化、反硝化和固氮由特定的酶催化，这些酶对环境干扰和污染敏感。 此外，氮管理是农业和废水处理中的一个重大挑战。 纳米材料的生产和在商业产品中的使用迅速增长，引起了人们对其对环境的潜在不利影响的担忧。 我们目前对微生物摄取和毒性机制的了解有限。 此外，大多数毒理学研究评估？制造材料？而不是经过环境改造后获得的形式。 我们将研究纯培养物以及财团中相关酶的调节，从而解决NSF任务中重要的问题，即生成理解和减轻NP与环境相互作用的潜在有害影响的预测方法。智力优势。 本研究将基于NP-细胞相互作用的特定性质（离子铜吸收与NP吸收;外部与内部溶解，随后产生活性氧（ROS）和膜/DNA/ATP损伤等），检验铜NP将选择性影响氮循环中涉及的细菌群落的种群、多样性和活性的假设。 虽然有一些最近的报告，对实验室纯培养的纳米粒子的短期毒性作用，这一建议的新方面，包括评估纳米粒子？对一类土著微生物的影响，以及它们在较长时间尺度上发挥的环境作用。 此外，这将是第一项探索高通量筛选（HTS）的研究，用于评估NP毒性的剂量-反应特征以及机制。 具体目标包括：（a）通过标准生理学和HTS测定确定铜NP的微生物影响，（B）研究铜NP对硝化细菌、反硝化细菌、厌氧氨氧化细菌和固氮细菌的几种纯培养物中功能基因表达的影响，以鉴定N循环中最敏感的微生物过程，和（c）量化和模拟N循环细菌群落的种群和多样性的变化，包括絮凝体内运输阻力对离子和颗粒铜、营养物和电子受体的可用性的影响。在纯培养物和微宇宙中，将使用酶特异性测定以及RT-qPCR来确定NP对相关基因表达的影响。 最终，本文采用的方法将作为一个模板，以解决NP危害识别和风险评估，安全设计和纳米技术的实施，以及全球碳和氮循环的管理。 拟议研究的更广泛影响超出了更好地了解NP与环境相关细菌的相互作用。 除了在科学会议上的出版物和演讲外，研究结果还将被翻译成一系列讲座，在环境生物技术的新研究生课程和环境纳米技术的重新设计的本科课程（均由PI教授）中提出。 此外，PI将与洛杉矶联合学区的一所中学合作，为新的环境科学课程开发课程，并在Go绿色园艺俱乐部开展实践活动，以描述细菌在环境循环中的作用，并评估有毒化学品的影响。 最后，PI将担任女性工程师协会（SWE）加州大学洛杉矶分校分会的教师顾问，并与资助的博士一起参与。学生，在会议和推广活动。

1134355MahendraThis NSF award by the Environmental Health and Safety of Nanotechnology program supports work by Professor Shaily Mahendra to examine the effects of copper nanoparticles (NPs) on the diversity and function of bacteria involved in nitrogen cycling in natural and engineered environmental systems.Background and Significance. We anticipate that in the next few decades, the inputs of engineered nanomaterial-containing products to waste streams will increase, and more plants will be required to carry out tertiary treatment of wastewater. Transformations of nitrogen in the environment are microbially driven; nitrification, denitrification, and nitrogen fixation are catalyzed by specific enzymes, which are sensitive to environmental disturbances and pollution. Additionally, nitrogen management is a significant challenge in agriculture and in wastewater treatment. The rapid growth in production and use of nanomaterials in commercial products has raised concerns about their potential adverse effects on the environment. Our current understanding of the mechanisms of uptake and toxicity towards microorganisms is limited. Furthermore, most toxicological studies evaluate ?manufactured materials? rather than the forms attained after undergoing environmental transformations. We will investigate the regulation of relevant enzymes in pure cultures as well as consortia, thus, addressing issues important to NSF missions of generating a predictive methodology of understanding and mitigating the potential harmful effects of the interaction of NPs with the environment. Intellectual Merits. This study will test the hypothesis that copper NPs will selectively affect the population, diversity, and activity of bacterial communities involved in nitrogen cycling based on specific nature of NP-cell interactions (ionic copper uptake versus NP uptake; external versus internal dissolution followed by reactive oxygen species (ROS) generation and membrane/DNA/ATP damage; etc.). While there are a few recent reports of short-term toxic effects of NPs on laboratory pure cultures, the novel aspects of this proposal include evaluating NPs? effects on a class of indigenous microorganisms, and the environmental roles they play, over longer time scales. In addition, this will be the first study to explore high-throughput screening (HTS) for evaluating dose-response characteristics as well as mechanisms of NP toxicity. Specific objectives include: (a) to determine the microbial impacts of copper NPs via standard physiological and HTS assays, (b) to investigate the effect of copper NPs on functional gene expression in several pure cultures of nitrifying, denitrifying, anammox, and nitrogen-fixing bacteria in order to identify most susceptible microbial process in the N cycle, and (c) to quantify and model changes in population and diversity of N-cycling bacterial communities, including the effect of intrafloc transport resistance on availability of ionic and particulate copper, nutrients and electron acceptors. pure cultures and microcosms, effect of NPs on the expression of relevant genes will be determined using enzyme-specific assays as well as RT-qPCR. Ultimately, the methodology employed herein will serve as a template to address NP hazard identification and risk assessment, safe design and implementation of nanotechnology, as well as management of global carbon and nitrogen cycles.Broader Impacts. The broader impacts of the proposed research extend beyond a better understanding of NP interactions with environmentally relevant bacteria. In addition to publications and presentations at scientific meetings, the findings will be translated into a series of lectures to be presented in a new graduate course on Environmental Biotechnology and a redesigned undergraduate course on Environmental Nanotechnology (both taught by the PI). Further, the PI will collaborate with a middle school in Los Angeles Unified School District to develop curriculum for a new environmental science class as well as hands-on activities in the Go Green horticultural club to describe the role of bacteria in environmental cycling of essential elements and assessing the impacts of toxic chemicals. Finally, the PI will serve as the faculty adviser for UCLA chapter of the Society of Women Engineers (SWE), and participate, with the funded Ph.D. students, in meetings and outreach activities.