Linking microbiology to past, present, and future geochemical cycles (LINK)

微生物在地球生物地球化学循环中扮演着催化剂的角色，是全球变化的推动者。反过来，生物地球化学循环调节地球表面条件，推动生物进化。定义这种关系的本质及其复杂的反馈网络是地球和生物科学的重大挑战之一，并解决了基本的人文问题。我的研究项目将定义微生物群落和地球表面化学之间的关系，提高我们破译过去和模拟未来的能力。利用过程速率测量和深度测序工作，该提案将量化微生物生态系统服务，为微生物群落的代谢能力、多样性和结构如何影响生物地球化学循环提供直接信息。这将允许基于环境群落的生理学而不是孤立的实验室培养来定义模型，从而导致预测环境变化和生态系统管理的新能力。LINK将在微生物生态学和环境化学研究的前沿创造知识，与加拿大自然和工程环境的管理直接相关（如鱼栏、废水处理设施、油砂、森林土壤、北极苔原和沿海水道）。*LINK将回答以下四个研究问题：*1：硝酸盐向铵的异化还原（DNRA）如何影响N循环，以及负责的生物体的生理能力是什么？DNRA是氮循环中的一个短路，限制了氮向大气的转移，其定量作用尚不清楚，有关DNRA的生理信息也很少。对DNRA的研究可能会产生巨大的影响，例如，在农业用地和水道氮污染的管理方面。*2：绿色硫细菌光合氧化铁是否能驱动早期地球的环境生产力和带状铁地层的沉积？这种光铁营养背后的遗传学是什么？30亿年来，海洋中含有大量亚铁，但今天这种情况很少见。我们对这些生态系统的功能知之甚少，也缺乏早期生物进化的生态背景。我从一个含铁湖泊中分离出了第一个远洋光养铁生物，它是含铁生态系统的主要生产者。对这种分离物的生理和遗传学研究将为了解光铁营养细菌在地球化学和生物进化中所起的作用提供新的线索。*3: Cr同位素揭示了大气和海洋的什么化学变化？铬同位素正在成为一种强有力的古氧化还原指标。Cr同位素分馏的机制仍然不明确，Cr同位素随时间的记录也很稀疏。对铬同位素分馏的了解将有助于了解大气和海洋化学的发展，以及生物进化的驱动因素。*4：关于过去的气候、微生物进化和含铁生物圈，图乌提湖的沉积物告诉了我们什么？国际大陆科学钻探计划选择印度尼西亚古图乌提湖作为重建印度-太平洋地区演化和气候历史的重中之重。热带气候具有全球影响，特别是在加拿大，那里的厄尔尼诺Niño事件调节了北极的温度、降水和海冰覆盖。保存在Towuti沉积物中的古代DNA记录了含铁微生物群落的进化模式，为研究含铁环境下的长期生物地球化学转变提供了一扇窗口，这是古代含铁岩石的宝贵模拟物。

Microbes act as agents of global change through their role as catalysts in Earth's biogeochemical cycles. Biogeochemical cycles, in turn, regulate Earth surface conditions, driving biological evolution. Defining the nature of this relationship and its complex feedback network is one of the grand challenges in Earth and Biological Sciences and addresses fundamental humanistic questions. My research program will define relationships between microbial communities and earth surface chemistry, improving our capacity to decipher the past and model the future. Using process rate measurements and deep sequencing efforts, this proposal (LINK) will quantify microbial ecosystem services, providing direct information on how the metabolic capacity, diversity, and structure of microbial communities influences biogeochemical cycling. This will allow the definition of models based on the physiology of environmental communities as opposed to isolated lab cultures, leading to new capacity for forecasting environmental change and ecosystem management. LINK will create knowledge at the forefront of research on microbial ecology and environmental chemistry with direct relevance to the management of natural and engineered environments in Canada (e.g. fish corrals, wastewater treatment facilities, Oil sands, forested soils, Arctic tundra, and coastal waterways). *LINK will answer four research questions, as outlined below:*1: How does dissimilatory reduction of nitrate to ammonium (DNRA) influence the N cycle, and what are the physiological capabilities of the responsible organisms? The quantitative role of DNRA, a short circuit in the N-cycle limiting nitrogen transfer back to the atmosphere, is unknown and physiological information on DNRA is scarce. Research into DNRA has the potential for huge implications, for example, in the management of agricultural land and nitrogen contamination in waterways.*2: Could Green Sulfur Bacteria photosynthetically oxidizing iron drive environmental productivity on the early earth and the deposition of Banded Iron Formations, and what are the genetics behind this photoferrotrophy? For 3 billion years, the oceans contained lots of ferrous iron, but today these conditions are rare. We know little about how these ecosystems function and have scant ecological context for early biological evolution. I have isolated the first pelagic photoferrotroph, the primary producer in ferruginous ecosystems, from a ferruginous lake. Physiological and genetic studies of this isolate will yield new clues into the roles photoferrotrophic bacteria played in Earth's chemical and biological evolution.*3: What do Cr isotopes reveal about atmospheric and ocean chemistry through time? Chromium isotopes are emerging as a powerful paleoredox proxy. Mechanisms for Cr isotope fractionation remain poorly defined, and the record of Cr isotopes through time is sparse. Knowledge on Cr isotope fractionation will yield insight into the development of atmospheric and ocean chemistry, drivers of biological evolution.*4: What do Lake Towuti's sediments tell us about past climate, microbial evolution, and the ferruginous biosphere? The International Continental Scientific Drilling Program has selected ancient Lake Towuti, Indonesia as its top priority for reconstructing the evolutionary and climate history of the Indo-Pacific Zone. Tropical climate has a global influence, particularly in Canada, where El Niño events modulate temperature, precipitation, and sea ice cover in the Arctic. Ancient DNA preserved in Towuti's sediments records evolutionary patterns of ferruginous microbial communities, offering a window into long-term biogeochemical transformations in ferruginous settings, an invaluable analogue for ancient ferruginous rocks.