The molecular signature of sulfide: Biomarkers of sulfur-oxidizing autotrophs

地球历史上的缺氧环境是人们激烈研究和争论的主题。低温硫氧化还原梯度是这些古环境的诊断特征。在现代环境中，硫氧化剂微生物分布在氧化还原梯度中，其种类极其多样，至少起源于7个主要的原核生物谱系。这些微生物的脂质特征尚不清楚，但作为潜在的分子化石（生物标志物）具有很大的兴趣。该项目旨在填补关于低温硫氧化型石养生物的脂质组成和生态特性的缺失信息。这项工作收集的数据将对代表地球演化主要生物和地球化学基准的古代缺氧环境的研究具有重要意义，如产氧光养生物的初始出现、地球表面的全球氧化、新元古代雪球地球事件、二叠纪/三叠纪灭绝和其他全球海洋缺氧时期。研究来自于光和无光现代硫化物梯度的样品将建立一个生态和生物地球化学背景，用于解释整个地质记录中硫化物环境中的有机生物特征。它还将有助于对微生物如何在微生物主导的生态系统（如早期地球上的生态系统）中组装的基本生态学理解。该项目支持我们的长期目标，即在环境中丰富的微生物中的脂质化学，脂质合成途径的进化和脂质分子化石的地质记录之间建立更强的联系。研究生和本科生的指导是该项目的核心，该项目将支持2名博士生和6名暑期本科生研究生。该项目还将涉及4名机械和电气工程专业的本科生，他们将通过宾夕法尼亚州立大学的学习工厂完成高级顶点项目。研究成果将以“地球缓存”的形式向公众传播，这是一种网络组织的地理挑战游戏，可以传达有关微生物多样性、进化、深度时间、生物地球化学循环和环境质量的特定地点信息。

EAR0525503Anoxic environments in earth's history are the subject of intense research and debate. Low temperature sulfur redox gradients are a diagnostic feature of these paleoenvironments. Microbial sulfur-oxidizers populating redox gradients in modern environments are extremely diverse, originating in at least 7 major prokaryotic lineages. The lipid signatures of these microorganisms are poorly known, but are of great interest as potential molecular fossils (biomarkers). The proposed project targets missing information about lipid compositions and ecological characteristics of low-temperature sulfur-oxidizing lithoautotrophs. Data gathered in this work will have significance for studies of ancient anoxic environments representing major biological and geochemical benchmarks in earth's evolution such as the initial appearance of oxygen-producing phototrophs, the global oxidation of the surface earth, Neoproterozoic snowball earth events, the Permian/Triassic extinction, and other periods of global ocean anoxia. Study of samples from photic and aphotic modern sulfide gradients will establish an ecological and biogeochemical context for interpreting organic biosignatures in sulfidic environments throughout the geologic record. It will also contribute basic ecological understanding of how microorganisms are assembled in microbially-dominated ecosystems such as those present on the early earth. This project supports our long-term goal of forging stronger links between the chemistry of lipids in microorganisms abundant in the environment, the evolution of lipid synthesis pathways, and the geologic record of lipid molecular fossils. Mentoring of graduate and undergraduate students is at the core of the project, which will support two Ph.D. students and 6 summer undergraduate research students. This project will also involve 4 undergraduate mechanical and electrical engineering undergraduate students doing senior capstone projects via Penn State's Learning Factory. Research results will be communicated to the general public in the form of "Earthcaches", web-organized geographical challenge games that convey site-specific information about microbial diversity, evolution, deep time, biogeochemical cycling, and environmental quality.