Resurrecting the Ancient Mechanism of Nitrogen Fixation
In a new study, NASA-supported researchers have shown that life on Earth found a way to access inorganic nitrogen early in its history, and has stuck with this method ever since. Life uses metabolic processes, or sets of chemical reactions that convert food into energy. The biosphere of our planet relies on key metabolic reactions to power cells, but scientists do not know if the same reactions have always been used throughout the history of life on Earth.
The new study focuses on how life is able to get nitrogen from inorganic sources, a process known as biological nitrogen fixation. Life on Earth depends on nitrogen, and has for billions of years.
Today, microorganisms are able to access biologically useful nitrogen from sources in the atmosphere using only one family of enzymes known as nitrogenases. Without nitrogenases, cells would not have the nitrogen they need to survive. However, nitrogen fixation is one of the most energetically challenging biochemical reactions found in nature.
For the first time, astrobiologists used a new approach to resurrect ancient nitrogenases in modern bacteria and showed that the ancestral nitrogenases still functioned similarly to modern enzymes. The study shows that life on Earth settled on this particular strategy for accessing inorganic nitrogen early in its history. Importantly, this approach allows astrobiologists to access extinct protein diversity, providing a window into how these essential metabolic processes have been selected for and maintained under past planetary conditions.
The study was performed at the University of Wisconsin – Madison by the MUSE team supported by the Interdisciplinary Consortia for Astrobiology Research (ICAR) program. The paper, “Nitrogenase resurrection and the evolution of a singular enzymatic mechanism,” was published in the journal eLife.