Molecular Mechanisms of Soluble Fe(III) Reduction by Metal-Reducing Members of the Genus Shewanella

希瓦氏菌属金属还原成员还原可溶性 Fe(III) 的分子机制

• 批准号: 0433941
• 负责人: Martial Taillefert
• 金额: $ 37.34万
• 依托单位: Georgia Tech Research Corporation
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2004
• 资助国家: 美国
• 起止时间: 2004-09-01 至 2008-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0433941&HistoricalAwards=false
• 关键词: Molecular; Mechanisms; Soluble; Fe; III

Iron is the fourth most abundant element in the Earth's crust and plays an essential role in the biogeochemical cycling of many elements. Yet little is known about microbially mediated Fe(III) reduction in anaerobic systems. Such reactions are to a wide variety of environmentally significant processes, including the biogeochemical cycling of Fe, Mn, trace elements, and phosphate; degradation of organic matter; weathering of Fe(III)-containing clays and minerals; and biomineralization of Fe(II)-bearing minerals such as magnetite. This work, which will be carried out by researchers at the Georgia Institute of Technology, strives to determine the molecular mechanism by which metal-reducing members of the genus Shewanella solubilize and subsequently reduce soluble Fe(III). Complementary genetic, biochemical, and in situ voltammetric approaches will be used to clone the Shewanella genes involved in solubilization and subsequent reduction of soluble Fe(III). The soluble Fe(III) reductases expressed from these genes will be analyzed for protein structural characteristics and electron donor oxidation and electron acceptor reduction activities via in situ voltammetry. The purified reductases will also be used as the antigen to generate soluble Fe(III) reductase antibodies for determining the subcellular location of the reductases in Shewanella. Soluble Fe(III) in natural environments may originate from Fe(III)-reducing bacteria which synthesize and excrete Fe(III)-solubilizing compounds. This work will provide the first evidence that Fe(III)-reducing bacteria play a significant role in the production of soluble Fe(III). Results from our proposed study will also demonstrate the importance of the solubilization of solid Fe(III) by Fe(III)-reducing bacteria in iron cycling. Because the bioavailability of Fe(III) depends on the crystallinity of solid Fe(III), the availability of exogenous chelators, or the abundance of active sites onto solid Fe(III), it is possible that Fe(III)-reducing bacteria adapt to their environmental conditions by using multiple Fe(III) reduction pathways. The proposed research will provide novel information on the genes and predicted gene products required to synthesize and excrete endogenous Fe(III)-solubilizing compounds and Fe(III) reductases. This information will be used in subsequent studies to determine the chemical composition of the solubilizing compounds and will provide insights into this possibility by focusing on a poorly studied pathway. Results from our study will help refine diagenetic models in which Fe(III) is assumed to be a reactive solid and may therefore have a significant impact on the fields of biogeochemistry. In terms of broader educational impacts, this study will engage students from two disparate, yet complementary disciplines who will combine their expertise to tackle a complex biogeochemical problem.

铁是地壳中第四丰富的元素，在许多元素的生物地球化学循环中发挥着重要作用。然而，对厌氧系统中微生物介导的Fe(III)还原知之甚少。这些反应涉及各种对环境有意义的过程，包括铁、锰、微量元素和磷酸盐的生物地球化学循环；有机物的降解；含铁粘土和矿物的风化；以及含铁(II)矿物(如磁铁矿)的生物矿化。这项工作将由佐治亚理工学院的研究人员进行，致力于确定希瓦氏菌属的金属还原成员增溶并随后还原可溶性铁(III)的分子机制。互补的遗传、生化和原位伏安方法将被用来克隆与可溶性Fe(III)的增溶和随后的还原有关的希瓦氏菌基因。这些基因表达的可溶性Fe(III)还原酶将通过原位伏安法分析蛋白质的结构特征以及电子供体氧化和电子受体还原活性。纯化的还原酶还将作为抗原产生可溶性Fe(III)还原酶抗体，用于确定希瓦氏菌中还原酶的亚细胞位置。自然环境中的可溶性Fe(III)可能来源于Fe(III)还原细菌，它们合成和分泌溶解Fe(III)的化合物。这项工作将首次提供证据，证明Fe(III)还原细菌在可溶性Fe(III)的生产中起着重要作用。我们拟议的研究结果也将证明铁(III)还原细菌对固体Fe(III)的增溶在铁循环中的重要性。由于Fe(III)的生物有效性取决于固体Fe(III)的结晶度、外源螯合剂的可用性或固体Fe(III)上活性中心的丰度，因此Fe(III)还原细菌可能通过多种Fe(III)还原途径来适应环境条件。这项拟议的研究将提供有关合成和排泄内源Fe(III)增溶化合物和Fe(III)还原酶所需的基因和预测的基因产物的新信息。这些信息将在随后的研究中用来确定增溶化合物的化学成分，并将通过关注一个研究较少的途径来提供对这种可能性的洞察。我们的研究结果将有助于完善成岩模型，其中Fe(III)被认为是一种活性固体，因此可能对生物地球化学领域产生重大影响。就更广泛的教育影响而言，这项研究将吸引来自两个不同但互补学科的学生，他们将结合他们的专业知识来解决复杂的生物地球化学问题。