Ecological and environmental influences on nitrogen fixation evolution

The evolution of ancient metabolisms played a pivotal role in shaping Earth into the habitable planet it is today. A prime example of this is biological nitrogen fixation (N₂-fixation), a metabolism that all life depends on. Unlocking the origin and evolution of N₂-fixation is imperative for understanding the processes that shape metabolic evolution on Earth. At the heart of N₂-fixation lies nitrogenase, an enzyme found only in prokaryotes and is the sole biological solution capable of reducing N₂ to NH₃^-. Its evolution is characterized by three distinct isozymes. The most ancient form utilizes a molybdenum-iron cofactor, while the others incorporate additional iron or vanadium in place of molybdenum. Yet, questions remain regarding how nitrogenase's evolution was influenced by its physical environment and ecological interactions. Here, we first examined the environmental drivers that shape the distribution and diversity of nitrogenase across today’s aquatic and terrestrial ecosystems. Then, we used ecological modeling to evaluate our hypothesis concerning the impact of resource availability on nitrogenase's evolution. Our results find that the expansion of habitats on early Earth likely spurred the evolution of nitrogenase’s isozymes, underscoring their coevolutionary journey with the environment. This work elucidates how the molecular evolution of critical metabolic innovations, like nitrogenase, is governed by their environmental and ecological surroundings, and offers insights applicable to other biogeochemically significant enzymes and metabolisms.

Primary Presenter: Morgan Sobol, University of Wisconsin - Madison (msobol@wisc.edu)

Authors:

Morgan Sobol, Department of Bacteriology, University of Wisconsin - Madison  (msobol@wisc.edu)

Amanda Garcia, Department of Bacteriology, University of Wisconsin - Madison  (akgarcia3@wisc.edu)

Holly Rucker, Department of Bacteriology, University of Wisconsin - Madison  (hrucker@wisc.edu)

Cécile Ané, Department of Statistics, University of Wisconsin - Madison  (cecile.ane@wisc.edu)

Yang Kuang, School of Mathematical and Statistical Sciences, Arizona State University  (atyxk@asu.edu)

Ariel Anbar, School of Earth and Space Exploration, Arizona State University  (anbar@asu.edu)

Betül Kaçar, Department of Bacteriology, University of Wisconsin - Madison  (bkacar@wisc.edu)