Activity, Preservation and Fossilization of Cryptoendolithic Microorganisms in Antarctica

隐内石是一种寄生在岩石微小洞穴中的生物，这些洞穴为它们提供了保护，使它们能够在极端环境中生存，比如南极洲干谷寒冷干旱的沙漠。隐内岩化石保存了过去生物的形态和特征，因此为研究生物提供了一个独特的机会。生活史和环境。为了研究这些化石记录，需要更好地了解哪些环境条件允许这些化石形成。目前在干谷中存在的气候梯度使我们能够从温和到日益恶劣的环境中研究活的、死的和化石的隐壁岩；让我们了解生命的极限以及这些化石是如何形成的。该项目将研制仪器，以检测活微生物的生物活性，并进行实验室实验，以确定其生存的环境极限。该项目还将描述活的、死的和化石隐内生石的化学和结构特征，以了解它们是如何变成化石的。了解微生物是如何在南极洲这样寒冷干燥的环境中以化石的形式保存下来的，可以帮助改进用于在火星等行星上类似栖息地寻找和识别外星生命证据的方法。本项目包括研究生和本科生的培养。在南极洲干谷寒冷、干旱的陆地栖息地，人们对隐石器时代微化石及其形成过程知之甚少，那里的生物活动遗产以生物特征的形式可辨，包括无机材料和微生物化石，这些生物特征保存并表明了过去生物活动的痕迹。提出的工作的总体目标是：(1)确定微生物呼吸和有机物的生物降解速率如何控制微生物石化；(2)对微生物化石及其活体化石进行表征，阐明其石化机制。利用在日益严酷（更加寒冷和干燥）的气候梯度中收集的样本，包括活的、死的和化石的隐内生时代微生物，拟议的工作将：(1)开发一种用于野外的仪器，可以在原位测量隐内生时代栖息地的小浓度二氧化碳；(2)通过测量CO2演化和delta13C特征，进行培养实验，以确定含有活微生物、死微生物和化石微生物的样品中微生物活性的变化以及微生物活性的极限；(3)使用一套显微镜技术（CLSM, cryo-SEM, FIB-SEM，µ-XFM）来关联微生物活力和活性的实验室实验证据，并确定生物特征和微生物化石的化学和形态特征。这些样品中微生物群落的宏基因组调查将用于表征多样性的差异，确定特定微生物（如原核生物、真核生物）是否更有能力在这些恶劣的气候条件下生存，并证实这些微生物生存状态的微观观察。

Cryptoendoliths are organisms that colonize microscopic cavities of rocks, which give them protection and allow them to inhabit extreme environments, such as the cold, arid desert of the Dry Valleys of Antarctica. Fossilized cryptoendoliths preserve the forms and features of organisms from the past and thus provide a unique opportunity to study the organisms? life histories and environments. To study this fossil record, there needs to be a better understanding of what environmental conditions allow these fossils to form. A climate gradient currently exists in the Dry Valleys that allows us to study living, dead, and fossilized cryptoendoliths from mild to increasingly harsh environments; providing insight to the limits of life and how these fossils are formed. This project will develop instruments to detect the biological activity of the live microorganisms and conduct laboratory experiments to determine the environmental limits of their survival. The project also will characterize the chemical and structural features of the living, dead, and fossilized cryptoendoliths to understand how they become fossilized. Knowing how microorganisms are preserved as fossils in cold and dry environments like Antarctica can help to refine methods that can be used to search for and identify evidence for extraterrestrial life in similar habitats on planets such as Mars. This project includes training of graduate and undergraduate students.Little is known about cryptoendolithic microfossils and their formation processes in cold, arid terrestrial habitats of the Dry Valleys of Antarctica, where a legacy of activity is discernible in the form of biosignatures including inorganic materials and microbial fossils that preserve and indicate traces of past biological activity. The overarching goals of the proposed work are: (1) to determine how rates of microbial respiration and biodegradation of organic matter control microbial fossilization; and (2) to characterize microbial fossils and their living counterparts to elucidate mechanisms for fossilization. Using samples collected across an increasingly harsher (more cold and dry) climatic gradient that encompasses living, dead, and fossilized cryptoendolithic microorganisms, the proposed work will: (1) develop an instrument to be used in the field that can measure small concentrations of CO2 in cryptoendolithic habitats in situ; (2) conduct incubation experiments to target variations in microbial activity in samples containing living, dead, and fossilized microorganisms as well as limits to microbial activity by measuring CO2 evolution and delta13C signatures; and (3) use a suite of microscopy techniques (CLSM, cryo-SEM, FIB-SEM, µ-XFM) to correlate laboratory experimental evidence for microbial viability and activity and to identify the chemical and morphological characteristics of biosignatures and microbial fossils. A metagenomic survey of microbial communities in these samples will be used to characterize differences in diversity, identify if specific microorganisms (e.g. prokaryotes, eukaryotes) are more capable of surviving under these harsh climatic conditions, and to corroborate microscopic observations of the viability states of these microorganisms.