Collaborative Research: Elucidating the role of animal heme peroxidase and organic complexing agents in the formation of Mn oxides by a Roseobacter bacterium

合作研究：阐明动物血红素过氧化物酶和有机络合剂在玫瑰杆菌属细菌形成锰氧化物中的作用

• 批准号: 1322790
• 负责人: Colleen Hansel
• 金额: $ 21.7万
• 依托单位: Woods Hole Oceanographic Institution
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2013
• 资助国家: 美国
• 起止时间: 2013-09-01 至 2016-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1322790&HistoricalAwards=false
• 关键词: Collaborative; Research; Elucidating; role; animal

The cycling of manganese (Mn) and formation of manganese oxide minerals has sweeping environmental and health implications. Manganese is a micronutrient, responsible for the function of a broad range of essential enzymes including those involved in photosynthesis and destruction of toxic cellular oxidants. The oxidized forms of Mn, both soluble Mn(III) and Mn(IV)-based oxide minerals, are key players in the cycling and sequestration of carbon and metal contaminants. The direct and indirect activity of microorganisms is largely responsible for the formation of Mn oxide minerals, yet why and how these organisms produce these minerals remains unclear. Animal heme peroxidase (AHP) enzymes have been implicated in the oxidation of Mn(II) and formation of Mn oxides by a number of bacteria. Further, the formation of Mn oxides by some bacteria and fungi has been linked to superoxide, an oxygen radical, produced outside the cell. Reaction between Mn(II) and superoxide results in the formation of hydrogen peroxide and Mn(III), not Mn(IV) oxide minerals. Removal of the hydrogen peroxide allows for the precipitation of small Mn oxides, yet their growth to larger particles such as those found in the environment is impeded and appears dependent upon the presence of organic compounds produced by the organism. It is clear that the formation of Mn oxides involves a complex network of abiotic and biotic reactions involving protein(s), superoxide, and organic molecules. Accordingly, this project will unravel the relationship between AHP, superoxide, and organic molecules in the formation of Mn oxides by a marine bacterium within the abundant and widespread Roseobacter clade. The PIs will identify the role of AHP in Mn oxide formation by disrupting genes encoding three AHP enzymes in a Mn oxide forming bacterium and also inserting these same genes into a related bacterium that does not make Mn oxides. The PIs will compare and monitor the species of Mn, the levels of superoxide and hydrogen peroxide, and the presence and composition of Mn-binding organic molecules produced by the wild-type and genetically modified bacteria to unravel the conditions necessary for Mn oxide formation.Manganese is receiving increasing attention as a dominant control on the release of the greenhouse gas carbon dioxide from soils and sediments, as it is one of a select few compounds that can degrade recalcitrant carbon to more labile forms thus hindering its long-term sequestration and stabilization. Further, since the formation of Mn oxides requires particularly strong oxidants, Mn is now regarded as a promising paleoproxy where it may serve as a key indicator of high oxygen conditions on early Earth and other planets. Yet, a scientific understanding of the Mn cycle is fundamentally incomplete, with major knowledge gaps in the processes responsible for the formation of Mn oxide minerals. This project will obtain essential information helping to close these gaps, thereby improving predictive models of carbon cycling, aiding strategies for cleaning up contaminated ecosystems, and informing interpretations of the early Earth and extraterrestrial rock record. This project will also involve the PIs directly mentoring and assisting an MS graduate student and 3 undergraduate students in research associated with this project. Furthermore, the PIs will develop and host a summer workshop for K-12 teachers to introduce them to the field of geomicrobiology and assist them in the development of curriculum and in-class activities to translate this knowledge to students in the classroom.

锰(Mn)的循环和氧化锰矿物的形成具有广泛的环境和健康影响。锰是一种微量营养素，负责一系列关键酶的功能，包括那些参与光合作用和破坏有毒细胞氧化剂的酶。锰的氧化形式，包括可溶的锰(III)和基于锰(IV)的氧化物矿物，在碳和金属污染物的循环和封存过程中起着关键作用。微生物的直接和间接活动在很大程度上是氧化锰矿物形成的原因，但这些微生物产生这些矿物的原因和方式尚不清楚。动物血红素过氧化物酶(AHP)参与了许多细菌对Mn(II)的氧化和锰氧化物的形成。此外，一些细菌和真菌形成的锰氧化物与细胞外产生的一种氧自由基--超氧化物有关。锰(II)与超氧化物反应生成过氧化氢和锰(III)，而不是锰(IV)氧化物矿物。过氧化氢的去除允许小锰氧化物的沉淀，但它们生长成环境中发现的较大颗粒的过程受到阻碍，似乎取决于有机体产生的有机化合物的存在。显然，氧化锰的形成涉及一个复杂的非生物和生物反应网络，涉及蛋白质(S)、超氧化物和有机分子。因此，这个项目将揭开AHP、超氧化物和有机分子之间的关系，在丰富而广泛的玫瑰杆菌分支中，海洋细菌形成锰氧化物。PI将通过干扰氧化锰形成细菌中编码三种AHP酶的基因，并将这些相同的基因插入到不产生氧化锰的相关细菌中，来确定AHP在氧化锰形成中的作用。PIs将比较和监测锰的种类、超氧化物和过氧化氢的水平，以及野生型和转基因细菌产生的与锰结合的有机分子的存在和组成，以揭示形成氧化锰所需的条件。锰作为土壤和沉积物中温室气体二氧化碳排放的主要控制因素，正受到越来越多的关注，因为它是少数几种化合物之一，可以将顽固的碳降解为更不稳定的形式，从而阻碍其长期固定和稳定。此外，由于锰氧化物的形成需要特别强的氧化剂，因此锰现在被认为是一种很有前途的古代物，可以作为早期地球和其他行星高氧条件的关键指标。然而，对锰循环的科学理解从根本上是不完整的，在负责形成锰氧化物矿物的过程中存在着重大的知识空白。该项目将获得有助于缩小这些差距的基本信息，从而改进碳循环的预测模型，帮助制定清理受污染生态系统的战略，并为解释早期地球和外星岩石记录提供信息。该项目还将包括PI直接指导和协助一名硕士研究生和三名本科生进行与该项目相关的研究。此外，专业人员会为幼稚园至十二年级的教师举办暑期工作坊，向他们介绍地球微生物学的领域，并协助他们制订课程和进行课堂活动，把这些知识传授给课堂上的学生。