Activity, Preservation and Fossilization of Cryptoendolithic Microorganisms in Antarctica

隐形内石是一种生物，它们在微小的岩石洞穴中定居，这为它们提供了保护，并使它们能够生活在极端环境中，例如南极洲干燥山谷的寒冷、干旱的沙漠。化石的隐形内石保存了过去生物的形式和特征，从而为研究生物提供了独特的机会？生活史和环境。为了研究这一化石记录，需要更好地了解是什么环境条件允许这些化石形成。目前干燥山谷中存在气候梯度，这使我们能够研究从温和到日益恶劣的环境中活的、死亡的和化石的隐形石块；提供了对生命极限和这些化石是如何形成的洞察。该项目将开发检测活微生物生物活性的仪器，并进行实验室实验，以确定它们生存的环境极限。该项目还将表征活的、死亡的和化石的隐形石块的化学和结构特征，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等寒冷干燥的环境中作为化石保存下来的，有助于改进方法，用于搜索和识别火星等行星上类似栖息地存在外星生命的证据。这个项目包括对研究生和本科生的培训。人们对南极洲干燥山谷寒冷、干旱的陆地生境中的隐石器时代微化石及其形成过程知之甚少，在那里，可以通过生物特征的形式辨认出活动的遗产，包括保存和指示过去生物活动痕迹的无机材料和微生物化石。这项拟议工作的总体目标是：(1)确定微生物呼吸和有机物的生物降解率如何控制微生物石化；以及(2)表征微生物化石及其活的对应物，以阐明石化的机制。利用在越来越严酷(更冷和更干燥)的气候梯度上收集的样本，包括活的、死的和化石的隐石器时代微生物，拟议的工作将：(1)开发一种用于现场测量隐石器时代栖息地中少量二氧化碳浓度的仪器；(2)进行培养实验，通过测量二氧化碳释放和Delta13C特征来针对含有活的、死的和化石的微生物样本中微生物活动的变化以及微生物活动的限制；以及(3)使用一套显微镜技术(CLSM、低温扫描电子显微镜、FIB-扫描电子显微镜、µ-XFM)来关联微生物活性和活性的实验室证据，并识别生物特征和微生物化石的化学和形态特征。对这些样本中微生物群落的总基因组调查将被用来表征多样性的差异，确定特定的微生物(例如原核生物、真核生物)是否更有能力在这些恶劣的气候条件下生存，并证实对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.