Collaborative Research: Mechanism of Manganese(IV) Oxide Biomineralization by a Bacterial Manganese Oxidase

锰（Mn）是一种生物学上至关重要的元素，通过许多酶的使用来支持生命，包括那些在植物中产生氧气和保护许多生物体免受活性氧的酶。因此，锰循环-生物可利用的锰离子（Mn（II））和不溶性锰氧化物矿物（MnO 2）之间的相互转换-是全球性的重要。微生物在推动锰循环中发挥着重要作用：一些细菌使用MnO 2进行呼吸，在此过程中将矿物质转化为溶解的Mn（II），而其他细菌可以氧化Mn（II），形成在许多环境中可以发现的MnO 2沉积物。后一个过程，生物矿化，是一个了解较少的锰地球化学领域。凭借该奖项，布拉德利特博博士和托马斯斯皮罗博士将开发细菌氧化锰生物矿化的全面图片，这对于了解二氧化锰在自然界中的加工方式至关重要，以及这种见解如何应用于二氧化锰矿物在环境修复和生物能源生产中的新兴用途。该项目将加强对下一代科学家的培训，并开展外联活动，包括指导学生和旨在吸引服务不足/代表性不足的初中和高中学生学习科学专业的计划。将制作一套艺术插图，向更广泛的受众宣传该项目，并通过各种渠道提供。在许多Mn（II）氧化细菌中，多铜氧化酶（MCO）酶被认为是Mn（II）氧化的催化剂。在Mn（II）氧化芽孢杆菌属物种中，休眠孢子氧化Mn（II）并形成MnO 2矿物质，由位于孢子外壁（孢子周围的复杂结构）中的MCO催化。然而，二氧化锰生产的分子机制仍有待阐明。通过第一个纯化的细菌锰氧化复合物Mnx和一系列锰氧化细菌，该项目将揭示细菌如何控制MnO 2纳米颗粒的形成。具体来说，研究人员将描述蛋白质如何引导矿物质单位的形成，它们如何被驱逐到溶液中并进一步生长以形成自然界中发现的矿物质，以及自然环境的复杂性-整个细胞的生物物质，络合剂和溶解的铁-如何影响最终的生物矿物。该项目通过多种最先进技术的协作和集成方法得到高度利用，包括cryoEM，SAXS，EXAFS，液池TEM和计算方法，以提供氧化锰生物矿化的独特分子水平。此外，该项目将扩大使用最先进的显微技术，主要用于生物医学和材料科学研究，以解决地球化学意义的问题。该奖项反映了NSF的法定使命，并已被认为是值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估的支持。

Manganese (Mn) is a biologically vital element, supporting life through its use by many enzymes, including those that produce oxygen in plants and that defend many living organisms against reactive oxygen species. Thus, the manganese cycle—the interconversion between bioavailable Mn ions (Mn(II)) and insoluble Mn oxide minerals (MnO2)—is globally important. Microorganisms play a significant part in driving the manganese cycle: some bacteria use MnO2 for respiration, in the process converting the mineral to dissolved Mn(II), while other bacteria can oxidize Mn(II), forming the MnO2 deposits that can be found in many environments. The latter process, biomineralization, is a less-understood field in manganese biogeochemistry. With this award, Dr. Bradley Tebo and Dr. Thomas Spiro will develop a comprehensive picture of bacterial manganese oxide biomineralization, which is essential for understanding how MnO2 are processed in nature, and how this insight might be applied to the burgeoning uses of MnO2 minerals in environmental remediation and bioenergy production. The project will enhance the training of the next generation of scientists and embrace outreach activities, including mentoring students and programs that seek to attract underserved/underrepresented middle and high school students to science majors. A set of artistic illustrations to communicate the project to a broader audience will be created and made available through various channels.In many Mn(II)-oxidizing bacteria, multicopper oxidase (MCO) enzymes have been implicated to be the catalysts for Mn(II) oxidation. In Mn(II)-oxidizing Bacillus species, dormant spores oxidize Mn(II) and form MnO2 minerals, catalyzed by MCOs residing in the exosporium—a complex structure that surrounds the spores. However, the molecular mechanism of MnO2 production remains to be elucidated. With the first purified bacterial manganese oxidizing complex, Mnx, and a collection of manganese-oxidizing bacteria, this project will reveal how bacteria control the formation of MnO2 nanoparticles. Specifically, investigators will characterize how the protein guides the formation of mineral units, how they are expelled into the solution and further grow to form the mineral found in nature, and how complexities of natural environment—biological matter of whole cells, complexing agents, and dissolved iron—affect the final biomineral. The project is highly leveraged through a collaborative and integrated approach of multiple state-of-the-art techniques, including cryoEM, SAXS, EXAFS, liquid-cell TEM, and computational methods to offer a unique molecular-level view of manganese oxide biomineralization. Additionally, the project will expand the use of state-of-the-art microscopic techniques, primarily used in biomedical and materials science research, to address questions of geochemical significance.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.