The Kinetics of Microbial Sulfuric Acid Speleogenesis

微生物硫酸洞穴形成的动力学

• 批准号: 0617160
• 负责人: Philip Bennett
• 金额: $ 6.78万
• 依托单位: University of Texas at Austin
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2006
• 资助国家: 美国
• 起止时间: 2006-08-15 至 2010-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0617160&HistoricalAwards=false
• 关键词: Kinetics; Microbial; Sulfuric; Acid; Speleogenesis

EAR-0617160BENNETTThe Earth's subsurface contains innumerable habitats occupied by microorganisms that manipulate chemical forms of energy and alter the geologic surroundings to scavenge nutrients. These chemolithotrophic communities utilize energy from redox transformation of inorganic substrates, without an influx of reduced carbon or allochthonous macronutrients. For the last four years we have been characterizing the geochemistry and microbiology of Lower Kane Cave (LKC), a sulfidic carbonate cave ecosystem, as an accessible analog for deep subsurface environments. Here chemolithotrophic sulfur (S) oxidation forms the base of a complex microbial ecosystem, and these microbes appear to accelerate the oxidation of sulfide to sulfate, generating proton and potentially modifying their habitat by dissolving limestone. Our preliminary results suggest a much broader significance of terrestrial S-based microbial communities, raising new questions about subsurface ecosystems, S metabolism, the coupling of S and C cycles, and the geological consequences.Scientific Merit: Our previous work has established that a subsurface chemoautotrophic microbial population thrives in the sulfidic waters of LKC, oxidizing sulfide. Mass balance calculations show that the standard model of sulfuric acid speleogenesis (SAS), the volatilization of H2S and autoxidation on the cave wall, is insignificant, and almost all sulfide is oxidized in the aquatic system. Unanswered, however, is the question of whether the microbes accelerate sulfide oxidation and speleogenesis, directly participating in the geologic process of speleogenesis. We propose to use the natural laboratory of LKC, combined with controlled laboratory microcosm experiments, to examine the importance of microbial SAS as a mechanism of karstification. This proposal will address the following questions:1- How does the aquatic microbial community accelerate limestone weathering?2- Do the different SOB populations, with diverse S-oxidation mechanisms, influence limestone weathering to different degrees? Is community composition important?3- What is the importance of mineralogy to microbial habitat?Batch reactors and flow-through chemostat reactors will be used to examine selected monoculture and environmental mixed population community influence on calcite and dolomite dissolution rate. We will use the tools and techniques developed from our previous work at LKC to characterize the cave geochemistry, and the microbial communities in both the field system and the laboratory reactors using culture-independent methods. The rate measurements will then be combined with the detailed molecular microbiological characterization using SSU Rdna phylogenetics, RFLP, FISH and PLFA analysis to characterize the influence of community on karstification. Both the role of microbes in carbonate weathering, and the role of mineral chemistry in defining the habitat for these neutrophilic microbial populations will be examined.Broader Impacts: Sulfuric acid speleogenesis is potentially a widespread phenomenon that could be responsible for accelerated karstification and development of aquifer networks for regionally critical source of water, including the Edwards Aquifer of central Texas and its endemic stygobites and stygophiles. This project has implications for our understanding of the development of karst porosity for both aquifer and petroleum reservoirs, and our knowledge of subsurface microbial ecology. In particular this project will enhance our understanding of the role of mineralogy in microbial ecology, and allow a better understanding of the mechanisms for microbial survival and growth in the subsurface, with implications for pathogen transport in karst aquifers. This project will directly support one PhD, one MS, and one undergraduate student at the University of Texas, and introduce them to the developing field of microbial geochemistry and geomicrobiology. The LKC site has become a type locality for directly examining the theory of SAS in karstification, and the results from our previous research have been presented on PBS-NOVA, and rebroadcast by the BBC throughout Europe. The results from our work have also become a central theme in two graduate classes at UT, and the well characterized archived samples are used to teach molecular techniques to new graduate students in the geomicrobiology program

EAR-0617160BENNETT地球的地下有无数的栖息地，这些栖息地被微生物占据，这些微生物操纵化学形式的能量并改变地质环境以清除营养物质。这些化能自养群落利用无机底物氧化还原转化产生的能量，没有减少碳或异源大量营养素的流入。在过去的四年里，我们一直在描述下凯恩洞穴（LKC）的地球化学和微生物学特征，这是一个硫化碳酸盐洞穴生态系统，作为深层地下环境的可接近的模拟。在这里，化学营养硫（S）氧化形成了复杂的微生物生态系统的基础，这些微生物似乎加速了硫化物氧化成硫酸盐，产生质子并可能通过溶解石灰石来改变它们的栖息地。我们的初步结果表明，陆地基于硫的微生物群落具有更广泛的意义，提出了关于地下生态系统、硫代谢、硫和碳循环的耦合以及地质后果的新问题。科学优点：我们之前的工作已经确定，地下化学自养微生物种群在 LKC 的含硫水中繁衍生息，氧化硫化物。质量平衡计算表明，硫酸成穴（SAS）的标准模型，即H2S的挥发和洞壁上的自氧化，是微不足道的，几乎所有的硫化物在水生系统中都被氧化。然而，尚无答案的问题是微生物是否加速硫化物氧化和洞穴形成，直接参与洞穴形成的地质过程。我们建议利用LKC的自然实验室，结合受控实验室微观实验，来检验微生物SAS作为岩溶作用机制的重要性。该提案将解决以下问题：1-水生微生物群落如何加速石灰石风化？2-具有不同S-氧化机制的不同SOB种群是否会不同程度地影响石灰石风化？群落组成重要吗？3-矿物学对微生物栖息地的重要性是什么？间歇式反应器和流通式恒化反应器将用于检查选定的单一栽培和环境混合种群群落对方解石和白云石溶解速率的影响。我们将使用我们之前在 LKC 工作中开发的工具和技术，使用独立于培养的方法来表征洞穴地球化学以及现场系统和实验室反应器中的微生物群落。然后将速率测量与使用 SSU Rdna 系统发育学、RFLP、FISH 和 PLFA 分析的详细分子微生物学特征相结合，以表征群落对岩溶作用的影响。将研究微生物在碳酸盐风化中的作用，以及矿物化学在定义这些嗜中性微生物种群栖息地中的作用。更广泛的影响：硫酸成穴可能是一种普遍现象，可能导致加速岩溶作用和区域关键水源含水层网络的发展，包括德克萨斯州中部的爱德华兹含水层及其地方性含水层 stygobites 和 stygophiles。该项目对于我们了解含水层和石油储层岩溶孔隙度的发育以及我们对地下微生物生态学的了解具有重要意义。特别是，该项目将增强我们对矿物学在微生物生态学中的作用的理解，并更好地了解微生物在地下生存和生长的机制，对喀斯特含水层中的病原体运输具有影响。该项目将直接资助德克萨斯大学一名博士生、一名硕士生和一名本科生，并向他们介绍微生物地球化学和地球微生物学的发展领域。 LKC 站点已成为直接研究喀斯特作用中 SAS 理论的典型地点，我们之前的研究结果已在 PBS-NOVA 上发表，并由 BBC 在整个欧洲重播。我们的工作结果也成为 UT 两个研究生班的中心主题，并且经过充分表征的存档样本用于向地球微生物学项目的新研究生教授分子技术