Collaborative Research: Kinetics and Stable Isotopic Fractionation for Abiotic and Microbial Transformations of Elemental Sulfur at Seafloor Hydrothermal Environments

合作研究：海底热液环境中元素硫非生物和微生物转化的动力学和稳定同位素分馏

• 批准号: 1155346
• 负责人: David Fike
• 金额: $ 28.05万
• 依托单位: Washington University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-04-01 至 2016-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1155346&HistoricalAwards=false
• 关键词: Collaborative; Research; Kinetics; Stable; Isotopic

Elemental sulfur (So) is a key intermediate species for biochemical sulfur cycling in chimney deposits, the shallow subsurface in diffuse flow areas, and hydrothermal plumes at mid-ocean ridges. Although the floc found in the water column after a volcanic eruption is predominantly So and many microbial isolates from vents are found to utilize So, no significant reservoir of So has been found in chimney deposits, suggesting high turnover rates of elemental sulfur in the subsurface. The kinetic rate constants for abiotic So oxidation and reduction are unknown, even though they are critical for constraining the metastability, and thus bioavailability, of So in the presence of H2(aq) and O2(aq) at temperatures and pH conditions relevant to hydrothermal mixing environments. Nor have the rate constants describing microbial transformations of So been studied at environmentally relevant conditions. As a result, there is a discrepancy between predictions based on energetics and the observed physiology of microorganisms that have been isolated and grown in laboratory conditions. Accurate and realistic biotic and abiotic kinetic rate constants are essential for modeling biogeochemical transformations involving intermediate sulfur species and active microbial consortia at the variable pH and redox conditions found in subsurface underlying basalt- and ultramafic-hosted hydrothermal systems.In this project, researchers at Washington University of St. Louis (WU) and at the Carnegie Institute of Washington (CIW) will experimentally evaluate the kinetics of elemental sulfur abiotic oxidation/reduction at a range of T, pH and H2(aq)-O2(aq) concentrations relevant to the shallow subsurface of basalt and ultramafic hydrothermal systems: 250 bars, 40-120 deg C, pH 4 - 9, 0.1-20 mM H2(aq) and 0-0.25 mM O2(aq). Simultaneously, they will characterize the catabolic reaction rates of thre key bacterial species that mediate elemental sulfur redox transformations to determine if fractionation increases as environmental conditions begin to inhibit growth, as has been seen for SO4 reducing bacteria. By characterizing the geochemical and isotopic effect of So-oxidizing/reducing thermophilic autotrophs from vent systems, they expect to be able to evaluate the impact of complex subsurface microbial ecological systems on associated plume environments contributing to the global ocean sulfur cycle.Broader impacts: The proposed project brings together experimental, microbial, and sulfur isotope expertise, establishes a new collaboration between WU and the CIW, and reintroduces a female scientist back into full-time research by facilitating a leading role in this project. Two distinct undergraduate research projects crossing biology, geochemistry, and computer science will be supported. Furthermore, the research team will develop an online interactive simulation for secondary students that will allow them to use the real scientific data produced by this study in student-driven investigations. This educational outreach activity will also establish a working relationship with a secondary school teacher with experience adapting scientific data and methods for online learning.

元素硫（So）是烟囱沉积物、扩散流区浅层地下和大洋中脊热液羽流中硫生物化学循环的关键中间组分。虽然火山爆发后的水柱中发现的絮状物主要是SO和许多微生物分离物的通风口被发现利用SO，没有显着的水库，所以已被发现在烟囱存款，这表明高周转率的元素硫在地下。非生物的SO氧化和还原的动力学速率常数是未知的，即使它们是关键的约束亚稳定性，从而生物利用度，所以在H2（aq）和O2（aq）的存在下，在温度和pH值条件相关的水热混合环境。也没有速率常数描述微生物的转化，所以在环境相关的条件下进行了研究。因此，基于能量学的预测与在实验室条件下分离和生长的微生物的观察生理学之间存在差异。准确和现实的生物和非生物动力学速率常数对于模拟地下玄武岩和超镁铁质热液系统中存在的可变pH值和氧化还原条件下的生物地球化学转化至关重要。在本项目中，圣路易斯华盛顿大学（WU）和华盛顿卡内基研究所（CIW）的研究人员将在与玄武岩和超镁铁质热液系统的浅层地下相关的T、pH和H2（aq）-O2（aq）浓度范围内，通过实验评估元素硫非生物氧化/还原的动力学：250巴，40-120 ℃，pH 4 - 9，0.1-20 mM H2（aq）和0-0.25 mM O2（aq）。同时，他们将表征介导元素硫氧化还原转化的三种关键细菌物种的分解代谢反应速率，以确定分馏是否随着环境条件开始抑制生长而增加，如SO 4还原细菌所见。通过描述喷口系统中SO-氧化/还原嗜热自养生物的地球化学和同位素效应，他们预计能够评估复杂的地下微生物生态系统对相关羽流环境的影响，这些羽流环境有助于全球海洋硫循环。拟议的项目汇集了实验，微生物和硫同位素的专业知识，建立了WU和CIW之间的新合作，并通过在该项目中发挥主导作用，重新引入一名女科学家从事全职研究。两个不同的本科生研究项目交叉生物学，地球化学和计算机科学将得到支持。此外，研究小组将为中学生开发一个在线互动模拟，使他们能够在学生主导的调查中使用本研究产生的真实的科学数据。这一教育推广活动还将与一名中学教师建立工作关系，这名教师具有将科学数据和方法用于在线学习的经验。