Project: A microbe’s perspective on the marine nitrogen budget

During this project, PI Andrew Babbin will be investigating the availability of fixed nitrogen, predominantly in the forms of ammonium and nitrate. This fixed nitrogen 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.

The research group will work to 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 utilizes exquisitely controlled chemical and microbial compositions, seeding microbes into novel droplet-based microfluidic incubators. By integrating both environmental isolates and genetically modified mutants, the Babbin team 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.

[ Project description excerpted from: https://eapsweb.mit.edu/news/2019/microbes-perspective-marine-nitrogen-budget ]