Fig. 1: Protein phylogeny and age of resurrected ancestral nitrogenases (nifHDK).
From: Resurrected nitrogenases recapitulate canonical N-isotope biosignatures over two billion years
a Node colors represent the extant taxonomy. b Close-up of Group I nitrogenases. The ancestral nodes targeted in this study are labeled with circles. Heterocystous cyanobacteria (highlighted in teal) serve as a minimum age constraint for the ancestral nitrogenase nodes based on fossil evidence32. c Approximate ages for the origin of nitrogenase isoforms are based on geochemical12 and phylogenetic data29. The estimated timing of the origin of oxygenic photosynthesis and the Great Oxidation Event (GOE) are shaded in green and blue, respectively.
