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

微生物与矿物的相互作用是地球表面地球化学循环中无处不在的重要方面。在确定特定微生物群如何与矿物质，特别是铁氧化物相互作用方面取得了重大进展。然而，关于微生物如何制造和破坏单质硫（S(0)）的研究很少，尽管地质学家已经假设微生物参与了生产经济S(0)矿床。这一过程的化学和生物控制尚不清楚，需要更好地了解影响微生物生物膜内S(0)产生和消耗的因素。由于其独特的生物地球化学特征和人类探索的相对可及性，深地下Frasassi洞穴系统中的硫循环一直是之前几项研究的目标。洞穴生态系统是由发生在其永久硫化物和微氧含水层表面附近的微生物化学合成维持的。洞穴水中明显的白色生物膜含有20%至80%的单质硫。因此，它的地球化学和微生物特征使Frasassi成为研究微生物与硫循环中重要的固相中间体S(0)相互作用的有希望的系统。神秘的Epsilonproteobacteria来自全球分布和大部分未被培养的Sulfurovumales分支，是Frassasi生物膜的主要参与者。它们在高硫化物和低氧供应的水中尤其丰富，由于电子受体的可用性有限，这种条件应导致S(0)积累。利用Frasassi生物膜和富集培养作为模型系统，研究人员将超转录组学、相关电子显微镜和地球化学与现场和实验室实验相结合，以发展对S(0)积累生物膜群落的新认识。这项研究将提高对以下方面的认识：(1)微生物在生产地质S(0)矿床中的作用；（ii）微生物与固相S(0)相互作用的机理；（iii）目前未培养的Epsilonproteobacteria的代谢能力。该研究支持了整合现代和古代S生物地球化学的遗传和地球化学认识的长期目标。项目经费用于指导两名研究生和一名博士后。由于对洞穴和极端微生物的兴趣，拟议的项目为公众提供了很好的机会。该项目的图像和微生物培养将在两个非常成功的年度活动中使用：PSU勘探日和PSU地球科学系。“摇，摇，摇”。去年，超过2000名K-12学生和家长以及150名三年级学生参加了这些活动。微玻片培养项目将被纳入6-12年级的教师实践讲习班和地球、海洋与环境学院在刘易斯校区举办的年度海岸日活动，这是一个34年的传统，现在吸引了数千名社区成员。结果也将作为DE Sea Grant At Sea通讯的一部分，以及美国国家公共电台（NPR）的Sea Talk广播片段分享。

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.