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

古代沉积岩中的各种形态学、矿物学和地球化学特征已被用来破译地球上甚至其他行星上的生命和环境演化历史。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，我的研究计划将整合地球化学，微生物和遗传实验研究与现代热液泉和富铁湖泊的实地研究，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的组成部分。首先，我将研究各种细菌物种的表面反应性，从实验室培养和天然微生物垫，作为一种手段来评估特定的微量元素分配到生物质。更好地了解影响金属螯合的生物因素，不仅可以更有效地对受污染场地进行生物修复和对矿石金属进行生物回收（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地球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。预计通过这些比较分析，将获得新的见解，微生物活动和矿物吸附反应如何分配元素从前寒武纪海洋沃茨的底部沉积物，从而促进重建全球元素循环和进化的生物圈通过深时间。第三，我将评估微生物对自然界硅化作用的相对贡献，以及一些微生物对矿物结壳的反应。最终的目标是更好地了解微生物是如何进化的，是否存在进化偏见，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.