Modern microbe-metal-mineral interactions: testing for biosignatures in ancient rocks

古代沉积岩的各种形态、矿物学和地球化学特征已被用来破译地球上以及其他行星上生命和环境演化的历史。这些潜在的“生物特征”包括但不限于：带状铁地层（BIFs）和燧石中保存的微化石中微量元素和氧化还原敏感元素的相对丰度和同位素组成。正是在这方面，我的研究计划将把地球化学、微生物学和遗传学实验研究与现代热液泉和富铁湖泊的实地研究结合起来，以确定沉积物中指示微生物活动的特征。我的研究有三个具体组成部分。首先，我将从实验室培养物和天然微生物垫中研究各种细菌的表面反应性，作为评估特定微量元素在生物量上分配的手段。更好地了解影响金属固存的生物因素，不仅将有助于制定更有效的策略，对受污染地点进行生物修复和矿石金属的生物回收（这两者对加拿大工业和我们的环境都至关重要），而且微生物影响的沉积物中的微量元素分布也可能被证明是古代地球的可靠和强大的生物特征。其次，我将测量实验生产的铁矿物和BIF岩心的同位素和微量元素组成。预计通过这些对比分析，将对微生物活动和矿物吸附反应如何将前寒武纪海水中的元素划分到海底沉积物中获得新的见解，从而有助于重建全球元素循环和生物圈的深时间演化。第三，我将评估自然界中微生物对硅化的相对贡献，以及一些微生物对矿物结壳的反应。最终目标是更好地了解微生物是如何变成化石的，是否存在保存偏差，从而确定哪些微生物可能构成了我们最早的生命物理记录。

A variety of morphological, mineralogical, and geochemical characteristics in ancient sedimentary rocks have been used to decipher the history of life and environment in which it evolved here on Earth, and perhaps on other planets. These potential "biosignatures" include, but are not restricted to: the relative abundances and isotopic compositions of trace and redox-sensitive elements in banded iron formations (BIFs) and microfossils preserved in chert. It is this regard that my research programme will integrate geochemical, microbiological and genetic experimental studies with field-based research at modern hydrothermal springs and Fe-rich lakes to identify features in the sediments that are indicative of microbial activity. There are three specific components to my research. First, I will study the surface reactivity of various bacterial species, from both laboratory cultures and natural microbial mats, as a means to evaluate specific trace element partitioning onto biomass. A better understanding of biological factors influencing metal sequestration will not only enable more efficient strategies for bioremediation of contaminated sites and biorecovery of ore metals (both of which are of utmost importance to Canadian industry and our environment), but trace element distributions in microbial-influenced sediment may also prove to be reliable and robust biosignatures for ancient Earth. Second, I will measure isotope and trace element compositions in experimentally-produced iron minerals and BIF core. It is anticipated that through these comparative analyses new insights will be gained into how microbial activity and mineral adsorption reactions partitioned elements from the Precambrian ocean waters to the bottom sediment, thus facilitating reconstruction of global elemental cycling and evolution of the biosphere through deep time. Third, I will evaluate the relative contribution of microbes to silicification in nature, and how some microbes respond to mineral encrustation. The ultimate goal is to better understand how microbes fossilize, whether there exists preservational biases, and thus identify which microbes likely constituted our earliest physical record of life.