Investigating the formation of biogenic magnetite and the preservation of magnetofossils: implications for biosignatures and paleoenvironments

使用跨学科的方法，集成矿物学，地球化学和微生物学和电子显微镜的应用，我调查的过程，导致生物矿物的形成和表征其化学和同位素组成，晶体形态和矿物结构。总的来说，通过了解生物矿化的过程和途径，我们可以深入了解生物在地球化学循环中的作用。生物矿物作为生命史和环境信息的档案，可用于（i）作为古陆地和地外地质系统的生物特征，（ii）了解生命和生物圈的起源和演化，以及（iii）为重建古环境和古气候提供信息。我目前的研究计划是针对调查细菌产生的磁铁矿晶体，以提高矿物学和地球化学标准，区分生物和非生物磁铁矿。这是通过（1）分析新发现的古新世-始新世热极期（PETM）沉积物中的巨型生物成因磁铁矿及其与其他铁矿物（如磁铁矿）的关系，以及（2）研究从淡水湖泊和海洋栖息地收集的培养的趋磁细菌和磁性细菌及其磁铁矿化石（即，磁化石）。由于PETM被描述为一个极端的全球变暖事件，在大约55.5 Ma时，温度在180 ky的时间间隔内增加了约5 - 9°C，因此对PETM中生物磁铁矿的研究可能会对这一时期的古环境条件提供新的认识。它还对“人类世”（目前的全球时间）期间人为全球变暖的可能后果产生影响，因为PETM是目前的理想模拟。

Using an interdisciplinary approach that integrates mineralogy, biogeochemistry and microbiology and the application of electron microscopy, I investigate processes that lead to the formation of biominerals and characterize their chemical and isotopic composition, crystal morphology and mineral structure. In general, by understanding the processes and pathways of biomineralization, we gain valuable insight into the role of biology in geochemical cycles. Biominerals as archives of life history and environmental information can be used (i) as biosignatures in ancient terrestrial and extraterrestrial geological systems, (ii) to understand the origin and evolution of life and the biosphere, and (iii) to provide information for reconstructing paleoenvironments and paleoclimates. My current research program is directed towards investigating magnetite crystals produced by bacteria in order to improve the mineralogical and geochemical criteria to distinguish between biogenic and non-biogenic magnetite. This is accomplished by (1) analyzing the newly discovered giant biogenic magnetite present within sediments of the Paleocene-Eocene Thermal Maximum (PETM) and their relationship to other Fe minerals such as glauconite, and (2) studying the structural details of magnetosomes from both cultured magnetotactic bacteria and magnetic bacteria collected from freshwater lakes and marine habitats as well as their magnetite fossils (i.e., magnetofossils). As the PETM is characterized as an extreme global warming event where temperatures increased by about 5 to 9°C over an interval of 180 ky at about 55.5 Ma, investigation of the biogenic magnetite in the PETM may shed new light on the paleoenvironmental conditions of this period. It also has implications for the possible consequences of man-made global warming during the "Anthropocene" (the present age of global time) as the PETM is an ideal analogue for the present.