Collaborative Research: Tracking chemical, isotopic, and molecular signatures of tightly coupled sulfur cycling in phototrophic and chemosynthetic microbial ecosystems

微生物的代谢活动支配着地球地质时期的生物地球化学演化。试图了解全球生物地球化学的科学家面临的一个基本问题是：微生物群落组成（谁在那里？）、代谢活动（它们在做什么？）和环境条件（如pH值、硫酸盐水平）（它们是如何受到影响的？）之间的关系是什么？硫循环，特别是硫酸盐还原和硫化物氧化之间的耦合，是当今许多不同微生物生态系统中驱动碳矿化的主要地球化学途径之一。从古代岩石中恢复的同位素和矿物学证据表明，生物硫酸盐还原在早期地球上也发挥了重要作用。为了更好地了解这一全球重要的过程和活性硫循环微生物的相应生物特征，我们提出了一个多学科、高分辨率的地球化学和分子生物学研究，在三个具有代表性的微生物生态系统中密切耦合的微生物硫循环。其中包括3-4个成员的协同无氧光养联盟，适度多样化的化学合成硫氧化垫，以及高度复杂的底栖氧气光合微生物垫。这些系统在生物复杂性和主要硫循环途径方面有所不同，这将共同提供有关光依赖性和非依赖性硫代谢的基本信息。我们的工作结合了高空间(？Ým-scale)利用次级离子质谱（SIMS）和FISH-nanoSIMS、微伏安硫种测量和CARD-FISH分子成像技术对硫和碳同位素数据进行分辨率分析，以研究微生物空间组织、代谢活动之间的联系，并通过耦合硫循环群落建立地球化学梯度。结合实验室和现场研究的数据，将开发出一套新的工具集，可用于在微生物主导的沉积环境中以前所未有的规模研究紧密耦合的硫循环。这个项目将告诉科学家关于过去和现在环境中控制硫的基本化学和生物学。这很重要，因为硫不仅在控制我们如何看待这个星球上的生命进化的过程中起着关键作用，而且在作为金属资源来源的矿床，石油和天然气的形成及其经济复苏，影响作物产量和水资源质量的土壤养分有效性，以及地下水和地表水中许多污染物的运输中起着关键作用。此外，该项目将有助于培养具有科学技术知识的下一代科学家，以便在高科技和科学产业，研究和教育领域工作。

The metabolic activity of microorganisms dominates the biogeochemical evolution of the Earth over geologic time. One of the fundamental questions facing scientists seeking to understand global biogeochemistry is: What is the relationship between microbial community composition (who¡¦s there?), metabolic activity (what are they doing?), and ambient environmental conditions (e.g., pH, sulfate levels) (how are they impacted?). Sulfur cycling, particularly the coupling between sulfate reduction and sulfide oxidation, is one of the dominant geochemical pathways driving carbon mineralization within many diverse microbial ecosystems today. Isotopic and mineralogical evidence recovered from ancient rocks suggest biological sulfate reduction played an important role on early Earth as well. In attempt to better understand this globally important process and the corresponding biosignatures of active sulfur cycling microorganisms, we are proposing a multi-disciplinary, high-resolution geochemical and molecular biological investigation of closely coupled microbial sulfur cycling in three representative microbial ecosystems. These include a 3-4 member synergistic anoxygenic phototrophic consortium, moderately diverse chemosynthetic sulfur-oxidizing mats, and highly complex benthic oxygenic photosynthetic microbial mats. These systems differ in terms of biological complexity and in the major sulfur cycling pathways, that collectively will provide fundamental information regarding light-dependent and -independent sulfur metabolisms. Our work combines analyses at high spatial (?Ým-scale) resolution of sulfur and carbon isotopic data using secondary ion mass spectrometry (SIMS) and FISH-nanoSIMS, microvoltammetic sulfur species measurements, and CARD-FISH molecular imaging to investigate the linkage among microbial spatial organization, metabolic activity, and establishment of geochemical gradients by coupled sulfur cycling communities. Together, the data from this combined laboratory and field study will develop a new toolset that can be used to study tightly coupled sulfur cycling on an unprecedented scale within microbially dominated sedimentary environments. This project will inform scientists about the fundamental chemistry and biology governing sulfur in the environment, past and present. This is important because sulfur plays a critical role in processes controlling not only how we view the evolution of life on this planet, but also about ore deposits as sources of metal resources, oil and gas formation and their economic recovery, soil nutrient availability affecting crop yields and the quality of water resources, and the transport of many contaminants in ground and surface waters. Additionally this project will help train the next generation of scientists with the scientific and technical knowledge to work in high tech and scientific industry, research, and education fields.