ECIMMEE Project: A Microbe’s Perspective on the Marine Nitrogen Budget
The availability of fixed nitrogen, predominantly in the forms of ammonium and nitrate, limits primary production across much of the global oceans. The standing stock of this bioavailable pool is in turn regulated by the balance of marine microorganisms producing ammonium from dinitrogen gas (diazotrophy) and reforming dinitrogen from nitrate and nitrite (denitrification). Strikingly, the specific factors regulating the rates and efficiency of nitrogen transformation processes remain poorly constrained.
We will unravel the complexities of the microbial nitrogen cycle to better understand the mechanisms by which these climatically critical bacteria reshape the chemical environment for themselves and for all marine organisms. The laboratory system developed here utilizes exquisitely controlled chemical and microbial compositions, seeding microbes into novel droplet-based microfluidic incubators. By integrating both environmental isolates and genetically modified mutants, we will systematically determine the range of conditions under which each nitrogen metabolic transformation can occur. Complementary chemostat experiments will extend the parameters extracted from the droplet-based batch cultures to real-world climate simulations and metabolic models. This approach to empirically and theoretically constrain the kinetic and thermodynamic characteristics of each nitrogen transformation step will enable a mechanistic framework of community nitrogen metabolism and species interactions. Through these targeted experiments and analyses, we will connect metabolic activities at the micro-scale to global nitrogen biogeochemistry.
Hailing from New Jersey, Andrew Babbin is a chemical oceanographer, biogeochemist and microbial ecologist. He is an assistant professor at the Massachusetts Institute of Technology in the Department of Earth, Atmospheric and Planetary Sciences. He and his group study how microorganisms interact with their chemical environment and with one another through the lens of marine nitrogen cycling. He espouses the intrigue and beauty of nitrogen chemistry daily to the dismay of his close carbon-focused colleagues who must endure being barraged by the inorganic nitrogen metabolic network. His reductionist mindset leads his lab to explore the fundamental characteristics of biogeochemical function, whereby systems can be simplified to their basal elements and complex behaviors described by their manageable mechanistic underpinnings. Babbin earned a bachelor’s degree in environmental engineering from Columbia University before returning to New Jersey to attend Princeton University for graduate school. At Princeton, he was first introduced to nitrogen biogeochemistry, and he never looked back. After graduating with a Ph.D. in 2014, Babbin moved to MIT to begin a National Science Foundation Postdoctoral Research Fellowship in Biology in the Department of Civil and Environmental Engineering. He began his faculty position in January 2017 and is currently a Doherty Assistant Professor in Ocean Utilization. When he’s not at sea, you can find him traveling the world, churning out pounds of fresh pasta, or playing semicompetitive softball.