The Kinetics of Microbial Sulfuric Acid Speleogenesis

地球的地下包含无数的栖息地，被微生物占据，它们操纵能量的化学形式，改变地质环境以吸收营养。这些化能无机营养群落利用无机基质的氧化还原转化产生的能量，而没有还原碳或外来大量营养素的流入。在过去的四年里，我们一直在表征下凯恩洞穴（LKC）的地球化学和微生物学，这是一个硫化碳酸盐洞穴生态系统，作为深层地下环境的一个可访问的模拟。在这里，化能无机营养型硫（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为硫酸盐，产生质子，并可能通过溶解石灰石来改变它们的栖息地。我们的初步研究结果表明，陆地S-为基础的微生物群落更广泛的意义，提出了新的问题，地下生态系统，S代谢，耦合的S和C的周期，和地质consequences.Scientific Merit：我们以前的工作已经建立了一个地下化能自养微生物种群蓬勃发展的硫化物沃茨的LKC，氧化硫化物。质量平衡计算表明，硫酸洞穴形成的标准模式（H2S的挥发和洞穴壁的自氧化）并不重要，几乎所有的硫化物都在水生系统中被氧化。然而，没有答案的问题是，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。我们建议使用LKC的自然实验室，结合受控的实验室微观实验，来研究微生物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-不同的硫氧化机制，不同的矿物群对石灰岩风化的影响程度不同吗？社区构成重要吗？3-矿物学对微生物栖息地的重要性是什么？间歇式反应器和流动恒化器反应器将被用来检查选定的单一文化和环境混合人口社区对方解石和白云石溶解速率的影响。我们将使用我们以前在LKC工作开发的工具和技术来表征洞穴地球化学，以及使用非培养方法在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序列遗传学、RFLP、FISH和PLFA分析的详细分子微生物学表征相结合，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，以及矿物化学在确定这些嗜盐微生物种群的栖息地方面的作用。硫酸洞穴形成是一种潜在的普遍现象，可能是加速岩溶作用和区域关键水源含水层网络发展的原因，包括德克萨斯州中部的爱德华兹含水层及其特有的stygobites和stygophiles。该项目对我们理解含水层和石油储层的岩溶孔隙度的发展以及我们对地下微生物生态学的了解具有影响。特别是这个项目将提高我们的矿物学在微生物生态学的作用的理解，并允许更好地了解微生物的生存和生长在地下的机制，在岩溶含水层中的病原体运输的影响。该项目将直接支持德克萨斯大学的一名博士，一名硕士和一名本科生，并向他们介绍正在发展的微生物地球化学和地质微生物学领域。LKC网站已成为一个典型的地方，直接检查岩溶SAS的理论，从我们以前的研究结果已提交PBS-NOVA，并通过英国广播公司在整个欧洲转播。我们工作的结果也成为UT两个研究生课程的中心主题，并且这些表征良好的存档样品被用于向地质微生物学课程的新研究生教授分子技术

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