Dimensions: Biodiversity of Iron-Respiring Microorganisms Fueled by a Cryptic Organic Sulfur Cycle

维度：由隐性有机硫循环推动的铁呼吸微生物的生物多样性

• 批准号: 1542596
• 负责人: Thomas DiChristina
• 金额: $ 26.24万
• 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: 2015
• 资助国家: 美国
• 起止时间: 2015-11-01 至 2017-10-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1542596&HistoricalAwards=false
• 关键词: Dimensions; Biodiversity; Iron; Respiring; Microorganisms

With a proof-of-concept award, this project will examine the diversity of microorganisms that breathe iron in place of oxygen. Since oxygen was absent on early Earth and iron-breathing bacteria are found near the root of the tree of life, they are likely to represent one of the first life forms that evolved on our planet. In the modern world, iron-breathing bacteria are important to many environmental and energy-generating processes, including release of iron nutrients to organisms residing in ocean and lake waters, degradation of hazardous pollutants in drinking water supplies, and electricity generation by bacteria. The biodiversity of iron-breathing bacteria in the environment, however, is poorly understood. Work by researchers at Georgia Tech will greatly expand our knowledge of these bacteria, and will test a novel hypothesis about how they breath iron. Since the iron rust particles are located outside the cell, generating energy by breathing iron rust particles requires novel strategies that this project will unravel. The hypothesis is that bacteria breathe iron rust particles and generate energy by producing sulfur molecules that are transferred outside the cell to interact with the external iron rust particles. Interaction between the sulfur compounds and the iron rust particles outside the cell results in energy production inside the cell. Experiments will involve examining the biodiversity of iron breathing bacteria in the salt marsh sediments of Skidaway Island (GA), which represents a coastal marine ecosystem replete with sulfur and iron. The research will also include training opportunities for women students from underrepresented groups in science at Alverno College in Milwaukee, WI. The proposed research will integrate state-of-the-art taxonomic (phylogenetic), genetic (metagenomic, metatranscriptomic), and functional (electrochemical, geochemical) approaches to determine the biodiversity of a previously overlooked microbial community linking the biogeochemical cycles of iron (Fe) and sulfur (S) in anaerobic marine and freshwater sediments. Initial geochemical and genetic findings indicate that bacterially-produced organic S (thiol) compounds can function as electron shuttles to deliver electrons to extracellular Fe(III) oxides, but the environmental significance of this activity is unproven. Since thiols are potent chemical reductants of Fe(III) oxides, yet are not detected in significant concentrations in sedimentary environments, these findings suggest that a cryptic organic S cycle fuels widespread microbial Fe(III) reduction activity in both freshwater and marine sediments. Field collections will be conducted at the salt marsh sediments of Skidaway Island (GA), which represents a coastal marine ecosystem replete with organic S and Fe. The overall experimental approach is divided into three main components: 1) identification of sediment layers displaying overlapping zones of Fe and organic S redox signals; 2) correlation of changes in gene expression profiles and the metabolic activity of organic S-driven Fe(III)-reducing bacteria and in perturbed sediment incubations; and 3) taxonomic (phylogenetic) and genetic (metagenomic, metatranscriptomic) analyses to determine the microbial community composition and functional gene expression patterns of pure (or highly enriched) cultures of organic S-driven Fe(III)-reducing bacteria. The project has the potential to transform a broad range of scientific disciplines by establishing a new link between organic S chemistry and microbial Fe metabolism through exploration of novel bacterial diversity. Microbial Fe(III) reduction is central to a wide variety of global processes, including the biogeochemical cycling of Fe (via reductive mobilization of insoluble Fe(III) oxides) and carbon (via anaerobic oxidation of organic matter). A large fraction of the flux of organic carbon remineralization in redox-stratified soils, peats, and freshwater and marine sediments has been attributed to microbial Fe(III) reduction, while microbially-catalyzed reductive dissolution of insoluble Fe(III) oxides may act a source of dissolved Fe to drive primary productivity in marine environments. A novel connection between the biogeochemical cycles of Fe, S, and C (potentially in a single bacterial cell) will revolutionize the current dogma concerning pathways for microbial Fe(III) reduction in the environment and will provide a new model for interpreting the global biogeochemical importance of microbial Fe(III) reduction. Microbial Fe(III) reduction is also central to a wide variety of other significant environmental and energy related processes, including reductive precipitation of toxic metals and radionuclides and generation of electricity in microbial fuel cells. If successful, this research will refine carbon cycling models (in which Fe(III) reduction is traditionally assumed to be a direct enzymatic process) and identify new diverse microorganisms for use in alternate strategies for remediation of radionuclide-contaminated aquifers and increasing power output in microbial fuel cells. Fe(III)-reducing microorganisms are also deeply rooted and scattered throughout the domains Bacteria and Archaea, an indication that microbial Fe(III) reduction may represent an ancient metabolic process. The phylogenetic link between microbial sulfur metabolism and Fe(III) reduction may therefore also have a significant impact on interpreting the evolutionary history and biodiversity of microbial respiratory systems. The research will broaden participation in science via educational opportunities for undergraduate students who are members of underrepresented groups in science.

通过概念验证奖，该项目将检查呼吸铁代替氧气的微生物的多样性。由于早期缺乏氧气，并且在生命之树的根部附近发现了呼吸细菌，因此它们可能代表了我们星球上进化的第一个生命形式之一。在现代世界中，铁呼吸细菌对许多环境和产生能源的过程很重要，包括将铁养分释放到居住在海洋和湖水中的生物，饮用水供应中有害污染物的降解以及细菌发电。然而，对环境中铁呼吸细菌的生物多样性知之甚少。佐治亚理工学院的研究人员的工作将大大扩展我们对这些细菌的了解，并将检验一个关于它们如何呼吸铁的新假设。 由于铁锈颗粒位于细胞外，因此通过呼吸铁锈颗粒产生能量需要该项目可以解散的新型策略。假设是细菌呼吸铁锈颗粒并通过产生在细胞外传递以与外部铁锈颗粒相互作用的硫分子来产生能量。硫化合物与细胞外铁锈颗粒之间的相互作用会导致细胞内部的能量产生。实验将涉及检查Skidaway Island（GA）的盐沼泽沉积物中铁呼吸细菌的生物多样性，该岛盐沼泽沉积物代表了沿海海洋生态系统充满硫和铁。这项研究还将包括威斯康星州密尔沃基市Alverno College的科学专业人数不足的女学生的培训机会。拟议的研究将整合最先进的分类学（系统发育），遗传学（宏基因组，元文字）和功能（电化学，地球化学）方法，以确定先前俯瞰的微生物群落的生物多样性，将生物地球化学循环（Fe）和硫磺（Fewer（fewer）和硫磺的生物地球化学循环链接起来）和硫磺（Sede）和硫磺（Sede）和硫磺（Sede）和硫磺（Sede）和sed s sed and and an ahobic and narobic and narobic。最初的地球化学和遗传发现表明，细菌生产的有机S（硫醇）化合物可以用作电子班车，以将电子传递到细胞外Fe（III）氧化物中，但是该活性的环境意义尚未证实。由于硫醇是Fe（III）氧化物的有效化学还原剂，但在沉积环境中尚未在显着浓度中检测到硫醇，因此这些发现表明，淡水和海洋沉积物中隐性有机S循环燃料的广泛微生物Fe（III）还原活性。田间收集将在Skidaway岛（GA）的盐沼泽沉积物进行，该沉积物代表了带有有机S和FE的沿海海洋生态系统。总体实验方法分为三个主要组成部分：1）鉴定沉积物层，显示了有机体和有机S氧化还原信号的重叠区域； 2）基因表达谱的变化和有机S驱动的Fe（III）还原细菌以及在扰动的沉积物孵育中的代谢活性的相关性；和3）分类学（系统发育）和遗传学（元基因组，元文字组）分析，以确定有机S驱动的Fe（III）纯化（或高度富集）培养物的微生物群落组成和功能基因表达模式。 该项目有可能通过探索新型细菌多样性来建立有机的化学与微生物FE代谢之间的新联系，从而改变广泛的科学学科。微生物FE（III）的还原是多种全球过程的核心，包括FE的生物地球化学循环（通过还原不溶性动员不溶性Fe（III）氧化物）和碳（通过有机物的厌氧氧化）。在氧化还原分层的土壤，泥炭以及淡水和海洋沉积物中，有机碳的通量很大一部分归因于微生物FE（III）的减少，而微生物催化的氧化氧化物的还原溶解（III）的氧化还能溶解不溶于作用（III）可能会成为溶解FE的源源于溶解型驱动力的一级产品。 Fe，S和C（可能在单个细菌细胞中）的生物地球化学循环之间的一种新颖的联系将彻底改变有关环境中微生物FE（III）减少途径的当前教条，并将为解释微生物FE（III）减少的全球​​生物地球化学重要性提供新的模型。微生物FE（III）的还原也是其他各种重要的环境和能量相关的过程，包括减少有毒金属和放射性核素的降水以及微生物燃料电池中的电力产生。如果成功的话，这项研究将完善碳循环模型（传统上假定为Fe（III）减少是直接的酶促过程），并鉴定出新的不同微生物，用于用于修复受放射性核酸酯污染的含水液的替代策略，以增加微生物燃料电池中的动力输出。 Fe（III）还原微生物也深深地根植并散布在整个域细菌和古细菌中，这表明微生物Fe（III）还原可能代表了古老的代谢过程。因此，微生物硫代谢与Fe（III）还原之间的系统发育联系也可能对解释微生物呼吸系统的进化史和生物多样性产生重大影响。 这项研究将通过教育机会扩大科学的参与，为科学领域代表性不足的成员的本科生。