Overview
- University of Wisconsin–Madison researchers led by Betül Kaçar and Ph.D. candidate Holly Rucker resurrected a roughly 3.2-billion-year-old nitrogenase and expressed it in living microbes for direct testing.
- Experimental measurements showed the enzyme’s nitrogen isotope fractionation matches that of modern nitrogenases, reinforcing long-used interpretations of the geological rock record over at least two billion years.
- Despite substantial sequence differences from present-day enzymes, the mechanism that sets the preserved isotopic signature appears conserved through deep time.
- The team applied synthetic biology and ancestral-sequence reconstruction, engineering strains such as Azotobacter vinelandii and quantifying isotope fractionation in cell biomass under controlled conditions.
- The peer-reviewed results, published January 22, 2026 in Nature Communications, strengthen astrobiology frameworks through the MUSE consortium for using nitrogen isotopes as a reliable biosignature and motivate studies of why the determining mechanism is conserved.