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

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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.