Collaborative Research: Genome-enabled Investigation of S(0) Cycling in a Subterranean Microbial Ecosystem

微生物-矿物相互作用是地球表面地球化学循环中无处不在且至关重要的方面。在确定特定微生物组如何与矿物质，特别是铁氧化物相互作用方面取得了重大进展。然而，关于微生物如何产生和分解元素硫(S(0))的研究很少，尽管地质学家假设微生物参与了经济S(0)矿床的形成。对这一过程的化学和生物控制还不是很清楚，需要更好地了解影响S(0)在微生物生物膜内产生和消耗的因素。深部地下弗拉萨西洞穴系统中的硫磺循环由于其独特的生物地球化学和相对易于人类探索的特点，一直是先前几个研究的目标。洞穴生态系统由微生物化学合成维持，微生物化学合成发生在其永久硫酸盐和微氧含水层表面附近。洞穴水中明显的白色生物膜含有20%至80%的元素硫。因此，它的地球化学和微生物学特征使Frasassi成为研究微生物与S(0)相互作用的一个很有前途的系统，S(0)是硫循环中重要的固相中间体。来自全球分布和大部分未培养的硫磺属分支的神秘的Epsilon蛋白细菌是Frassasi生物膜的主要参与者。它们在硫化物含量高、供氧量低的水域中尤其丰富，由于电子受体的可获得性有限，这些条件应该会导致S(0)的积累。以Frasassi生物膜和浓缩培养为模式系统，研究人员正在将元翻译、相关电子显微镜和地球化学与野外和实验室实验相结合，以期对S(0)积累的生物膜群落有新的认识。这项研究将加深对(I)微生物在地质S(0)矿床形成中的作用；(Ii)微生物与固相S(0)相互作用的机制；以及(Iii)目前未培养的变形表观杆菌的代谢能力。这项研究支持了整合遗传和地球化学对现代和古代S生物地球化学的理解的长期目标。项目资金用于指导两名研究生和一名博士后学者。由于对洞穴和极端微生物的兴趣，拟议的项目提供了接触普通公众的绝佳机会。来自该项目的图像和微生物培养将用于两个非常成功的年度活动：PSU探索日和PSU地球科学部。“摇动、摇摆、摇摆”。这些活动去年接触到了2000多名K-12学生和家长以及150名三年级学生。微幻灯片文化项目将被纳入到6-12年级的实践教师研讨会和地球、海洋与环境学院在刘易斯校园举行的一年一度的海岸日活动中，这是一个有34年历史的传统，现在吸引了数千名社区成员。结果也将作为DE Sea Grant at Sea时事通讯的一部分，以及NPR上的海洋谈话电台部分分享。

Microbial-mineral interactions are ubiquitous and crucial aspects of geochemical cycling at the Earth's surface. Significant progress has been made towards identifying how specific groups of microorganisms interact with minerals, especially Fe oxides. However, there has been little work on how microbes make and break elemental sulfur (S(0)), though geologists have postulated microbial involvement in producing economic S(0) deposits. Chemical and biological controls on this process are not well understood, and will require a better understanding of factors affecting S(0) production and consumption within microbial biofilms.Sulfur-cycling in the deep subsurface Frasassi cave system has been the target of several previous investigations due to its unique biogeochemistry and relative accessibility to human exploration. The cave ecosystem is sustained by microbial chemosynthesis taking place near the surface of its perenially sulfidic and microoxic aquifer. Conspicuous white biofilms in the cave waters contain 20 to 80% elemental sulfur by mass. Thus its geochemical and microbiological features make Frasassi a promising system for investigating microbial interactions with S(0), an important solid-phase intermediate in the sulfur cycle. Enigmatic Epsilonproteobacteria from the globally distributed and largely uncultivated Sulfurovumales clade are major players in Frassasi biofilms. They are especially abundant in waters with high sulfide and low oxygen supply, conditions which should lead to S(0) accumulation due to limited availability of electron acceptors. Using Frasassi biofilms and enrichment cultures as a model system, investigators are combining metatranscriptomics, correlative electron microscopy, and geochemistry with field and laboratory experiments to develop new understanding of S(0)-accumulating biofilm communities. This research will improve understanding of (i) the microbial role in producing geologic S(0) deposits; (ii) mechanisms for microbial interactions with solid phase S(0); and (iii) the metabolic capabilities of currently uncultured Epsilonproteobacteria. The research supports the long-term goal of integrating genetic and geochemical understanding of modern and ancient S biogeochemistry.Project funds provide for the mentoring of two graduate students and a postdoctoral scholar. The proposed project provides outstanding opportunities for outreach to the general public due to interest in caves and extreme microbes. Images and microbial cultures from the project will be utilized in two highly successful annual events: PSU Exploration Day and PSU Geosciences Dept. "Shake, Rattle, Rocks". These events reach more than 2000 K-12 students and parents last year and 150 third grade students. Project microslide cultures will be incorporated into a hands-on grade 6-12 teacher workshop and the College of Earth, Ocean and Environment's annual Coast Day on the Lewes campus, a 34-year tradition that now attracts thousands of community members. Results will also be shared as part of the DE Sea Grant At Sea newsletter, and Sea Talk radio segments on NPR.