A window on ancient systems: Understanding the environmental distributions of hopanoids using compound-specific multi-isotope analysis and metagenomics

技术概述：更好地了解hopanoid的现代来源和分布对于解释古代沉积记录至关重要。在这里，我们将使用跨学科的分析方法，即化合物特异性多同位素（13C， D/H和14C）测量结合分析参与藿烷类生物合成的功能基因，来解决海洋环境中藿烷类物质来源的问题。该项目将对类hopanoid同位素测量和DNA宏基因组进行系统调查。样本将覆盖从北极到热带的范围，三组样本将跨越三角洲到远洋沉积条件的梯度，形成微型样带。这些样品将允许使用在14C停留时间内建立的纬度模式和水源水的D/H来区分陆源和海洋源。已知的与不同类型微生物代谢相关的13C和D/H同位素分异模式将用于确定单个化合物的代谢来源，因为自养或异养代谢反映在同位素变异性中。hoppanoid生物合成基因（sqhC, hpnP, hpnR, hpnG, hpnH）的多样性将通过一种独立的方法与hoppanoid化合物分布有关，以测试局部生产是否与局部脂质组合沉积有关。一般重要性：保存在沉积岩中的有机分子提供了地球的记录？早期生物圈。它们帮助我们了解古代地球环境以及微生物群落的扩张、多样化和维持。这些化合物被称为“分子化石”，其中最早和最丰富的例子是被称为hopanoids的化合物。hopoid主要来源于细菌，在数十亿年的时间尺度上都可以检测到，并且被认为是地球上保存最丰富的分子之一。然而，到目前为止，我们对它们的环境、生理和/或物种起源缺乏全面的了解。本项目旨在回答海洋沉积环境中保存的藿类的基本问题。它们主要来自海洋，还是主要来自陆地？它们是否可能反映微生物分类群的特定亚群，或者它们是否广泛分布于不同的物种、栖息地和生活方式中？在这个项目中，我们将利用碳和氢同位素的自然分布来帮助回答这些问题。

Technical overview:A better understanding of the modern sources and distributions of hopanoids is essential for interpreting ancient sedimentary records. Here we will address questions of hopanoid provenance in marine settings using interdisciplinary analytical approaches, namely compound-specific multi-isotope (13C, D/H, and 14C) measurements combined with analysis of functional genes involved in hopanoid biosynthesis. The project will make a systematic survey of hopanoid isotope measurements and DNA metagenomes. The samples will cover locations ranging from arctic to tropical, and three sets of samples will span gradients of deltaic to pelagic depositional conditions, forming mini-transects. The samples will permit use of the established latitudinal patterns in 14C residence times and source water D/H to distinguish land-based from marine sources. Known patterns of 13C and D/H isotopic fractionation associated with different types of microbial metabolism will be used to determine the metabolic sources of individual compounds, because autotrophic or heterotrophic metabolism is reflected in isotopic variability. The diversity of hopanoid biosynthesis genes (sqhC, hpnP, hpnR, hpnG, hpnH) will be related to hopanoid compound distributions in an independent approach to test if local production is or is not related to local deposition of lipid assemblages. General importance:Organic molecules preserved in sedimentary rocks provide a record of Earth?s early biosphere. They help us understand ancient Earth environments and the expansion, diversification, and maintenance of microbial communities. Such compounds are called 'molecular fossils', and among the earliest and most abundant examples are compounds called hopanoids. Derived primarily from bacteria, hopanoids are detectable over timescales of billions of years and have been proposed to be among the most abundantly preserved molecules on Earth. However, to date we lack an overall picture of their environmental, physiological, and/or species origins. This project aims to answer basic questions about the hopanoids preserved in marine sedimentary environments. Are they primarily of marine origin, or do they come primarily from land? Are they likely to reflect particular sub-groups of microbial taxa, or are they broadly distributed among diverse species, habitats, and lifestyles? In this project we will use the natural distribution of the isotopes of carbon and hydrogen to help answer these questions.