Characterizing unexplored microbial habitats in oceanic crust along the South Atlantic Transect, IODP Exp. 390/393

该提案旨在为IODP Exp.期间回收的样本工作寻求资金。390/393 "南大西洋断面"（SAT），在此期间，在缓慢扩张的南大西洋中脊的西脊侧翼钻取了一个约7至61 Ma的玄武岩地壳断面。SAT的主要目标是加深我们对海脊侧翼热液流体-岩石反应以及大洋地壳内微生物生命的伴随分布和环境控制的了解。该项目将直接处理这些问题，采用有机地球化学与岩石学调查相结合的跨学科方法，研究海洋地壳内以前未探索的地壳微生物生境。拟议的工作将集中在沉积角砾岩，在所有恢复，除了最年轻的网站，在61 Ma老网站U1557的特殊恢复。类似的角砾岩发生在世界各地的各种海洋大地构造环境。因此，我们假设角砾岩构成了一个重要的，但迄今被忽视的组成部分，地壳深部生物圈。高渗透性的岩石为流体流动提供了充足的通道，从而为流体-岩石反应提供了充足的通道，这反过来又提供了生物燃料，从而促进了微生物的生命。在第一步中，我们计划结合联合收割机脂质生物标志物的调查，确定岩石蚀变的程度和风格的恢复角砾岩。在第二步中，地壳岩石的氧化状态将允许估计用于微生物生物质生产的生物可利用能量，然后我们将其与脂质生物质的实际分布相关联。脂质的详细结构表征将允许评估微生物群落的多样性是如何受到不断增加的基质年龄的影响，并将确定相应的栖息地的生理适应。化合物特定的稳定碳同位素将被用来确定潜在的微生物代谢从chemolithoautotrophic到异养的生活方式，后者可能会在较老的，更多的氧化，因此较少的能量产生的岩石中占主导地位。最后，热点的微生物生命将被可视化，并投入到空间关系的主机矿物基质的角砾岩在微米尺度上，利用国家的最先进的质谱成像结合micro-XRF。因此，该项目有望为目前深地壳生物圈研究的知识空白提供令人兴奋的新见解，并通过利用角砾岩海底未开发的地壳栖息地，将有助于完善对深生物圈的估计，并大大提高我们对地球上假定的最大微生物组的理解。

This proposal seeks funding to work on samples recovered during IODP Exp. 390/393 "South Atlantic Transect" (SAT), during which a transect from ~7 to 61 Ma old basaltic crust was drilled at the western ridge flank of the slow-spreading southern Mid-Atlantic Ridge. The primary goals of SAT were to further our understanding of ridge flank hydrothermal fluid–rock reactions and concomitant distributions and environmental controls of microbial life within the oceanic crust. This project will directly address these topics by using an interdisciplinary approach combining organic geochemical with petrological investigations to examine a previously unexplored crustal microbial habitat within the ocean crust. The proposed work will focus on sedimentary breccias that were recovered at all except the youngest sites with exceptional recovery at 61 Ma old Site U1557. Similar breccias occur worldwide in a variety of oceanic geotectonic settings. We therefore postulate that breccias constitute an important, but so far overlooked component of the crustal deep biosphere. The highly permeable rocks provide ample paths for fluid flow and hence for fluid-rock reactions, which in turn provides biofuels and hence fosters microbial life. In a first step we plan to combine lipid biomarker investigations of the recovered breccias with determining the extent and style of rock alteration. In a second step, the oxidation state of the crustal rocks will allow the estimation of bioavailable energy for microbial biomass production, which we will then relate to the actual distribution of lipid biomass. Detailed structural characterization of lipids will allow the assessment of how the diversity of microbial communities is affected by the increasing substrate age and will identify physiologic adaptations to the respective habitats. Compound specific stable carbon isotopes will be used to determine potential microbial metabolism shifts from chemolithoautotrophic to heterotrophic lifestyles, the latter of which may prevail in older, more oxidized and hence less energy-yielding rocks. Finally, hot spots of microbial life will be visualized and put into spatial relation with the host mineral matrix of the breccias on a micrometer scale by making use of state-of-the-art mass spectrometry imaging combined with micro-XRF. This project thus promises to provide exciting new insights into current knowledge gaps of deep crustal biosphere research and by tapping into the unexplored crustal habitat of brecciated seafloor, will help refine estimates of the deep biosphere and significantly advance our understanding of Earth’s presumed largest microbiome.