CARBON ISOTOPIC SIGNATURES OF MICROBIAL LIPIDS IN GEOTHERMAL DEPOSITS: ELUCIDATING THERMOPHILIC ECOLOGY

了解生命的起源和多样性是最具挑战性的科学努力之一。在这些努力中，限制地球上生命的极限是至关重要的，因为了解那些可以在极端温度，盐度或pH值的环境中生存甚至茁壮成长的生物体的生态学。最近，我们已经证明，微生物脂质是评估和重建陆地温泉的微生物学的有力工具。在这个建议中，我们专注于阐明地热生物的脂质的碳同位素签名。脂质生物标志物与稳定同位素分析相结合的使用对于了解微生物生态学至关重要，提供了微生物身份和生物化学过程之间的直接联系。脂质存在于所有生物体中，通常作为能量来源和细胞膜的结构成分。这些化合物通常具有高度的诊断性，在地质记录中保存完好，并夹带着生物多样性，环境条件和沉积后蚀变历史的信息，对于早期生命和天体生物学研究特别有吸引力。我们过去对地热矿床中生物标志物的研究揭示了封装脂质的深刻多样性，这些脂质可用于分析微生物群落组成。然而，我们以前的工作尚未开发的微生物岩保存的脂质的潜力是它们的碳同位素组成;在我们的数据的一个小子集中观察到脂质碳同位素值的强烈和高度不寻常的变化，但缺乏关键的背景数据（例如溶解无机碳的碳同位素组成，DIC，在池中）。这仍然是新西兰陶波火山区嗜热生理学和生态学以及那里形成的二氧化硅矿床的一个未开发的信息来源。这些存款是过去生活的重要档案，阐明在这样的设置有机质形成的控制将允许更好地解释保存在其中的OM组合。我们将绘制碳同位素值的范围，并评估其在不同的地热网站与不同的物理化学条件和不同的生物相的再现性。通过将这些数据嵌入温泉DIC碳同位素值和最近基于分子（DNA和RNA）方法的微生物群落分析的背景下，我们将解决不寻常的碳同位素组成的起源。这将极大地扩展我们的能力，解释生物标志物碳同位素值保存在古老的二氧化硅烧结，提供关键信息的来源，脂质生物标志物，代谢和营养结构。在这项工作中，我们将针对一系列的诊断化合物，从充分表征的地热环境中的陶波火山区在新西兰和探索碳同位素特征的变化的控制，耦合我们过去的生物标记为基础的解释碳同位素分析，以实现更好地了解地热环境的生物多样性，并解开地球化学和生态功能。这项工作将推进我们对岩石记录中保存的生物特征的解释，深入了解地球上最早生命形式的进化和生态，并为在太阳系其他地方寻找生命提供信息。

Understanding the origins and diversification of life represents one of the most challenging scientific endeavours. In such efforts, constraining the limits of life on Earth is vital, as is an understanding of the ecology of those organisms that can survive and even thrive in environments characterised by extremes of temperature, salinity or pH. Of particular interest are geothermal systems, populated by diverse and deeply-branching thermophilic bacteria and Archaea. Recently we have demonstrated that microbial lipids are powerful tools in assessing and reconstructing the microbiology of terrestrial hot springs. In this proposal we focus on elucidating the carbon isotopic signatures of the lipids of geothermal organisms. The use of lipid biomarkers in combination with stable isotope analysis is crucial to understanding microbial ecology, providing a direct link between microbial identity and biochemical processes.Lipids are found in all living organisms, typically serving as energy sources and structural components of cell membranes. Often highly diagnostic, well-preserved in the geological record, and entrained with information on biological diversity, environmental conditions and post-depositional alteration history, these compounds are particularly attractive for early life and astrobiological investigations. Our past studies of biomarkers in geothermal deposits reveal a profound diversity of encapsulated lipids, which can be utilized to profile microbial community composition. However, a potential of microbialite-preserved lipids that was untapped by our previous work is their carbon isotopic composition; strong and highly unusual variations in lipid carbon isotope values were observed in a small subset of our data but lacked crucial contextual data (e.g. the carbon isotopic composition of dissolved inorganic carbon, DIC, in the pools). This remains an untapped source of information on thermophilic physiologies and ecology in the New Zealand Taupo Volcanic Zone and the silica deposits formed there. Such deposits are essential archives of past life and elucidating the controls on organic matter formation in such settings will allow a better interpretation of the OM assemblages preserved in them. We will map the range of carbon isotope values and evaluate their reproducibility in various geothermal sites with differing physicochemical conditions and in different biofacies. By embedding this data in the context of thermal spring DIC carbon isotope values and recent microbiological community profiling based on molecular (DNA and RNA) approaches, we will resolve the origin of the unusual carbon isotopic compositions. This will greatly expand on our capacity to interpret biomarker carbon isotope values preserved in ancient silica sinters, providing crucial information on sources of lipid biomarkers, metabolism and trophic structure. In this work, we will target a range of diagnostic compounds from well-characterized geothermal settings in the Taupo Volcanic Zone in New Zealand and explore the controls on the variation of carbon isotopic signatures, coupling our past biomarker-based interpretations to carbon isotopic analyses in order to achieve a better understanding of the biodiversity of geothermal environments and to unravel biogeochemical and ecological function. This work will advance our interpretation of biosignatures preserved in the rock record, providing insight into the evolution and ecology of the earliest life-forms on Earth and informing the search for life elsewhere in the Solar System.