![\"Resurrection](\"https:\/\/cdn.sci.news\/images\/enlarge13\/image_14503e-Nitrogenase.jpg\")
<\/a><\/p>\nResurrection and characterization of ancestral nitrogenases. Image credit: Rucker et al., doi: 10.1038\/s41467-025-67423-y.<\/p>\n
University of Wisconsin-Madison\u2019s Professor Bet\u00fcl Ka\u00e7ar and colleagues focused on an enzyme called nitrogenase, which is critical to the process that converts atmospheric nitrogen into a form usable by living organisms.<\/p>\n
\u201cWe picked an enzyme that really set the tone of life on this planet and then interrogated its history,\u201d Professor Ka\u00e7ar said.<\/p>\n
\u201cWithout nitrogenase, there would be no life as we know it.\u201d<\/p>\n
Historically scientists have relied on evidence found in the geological record to build our understanding of past life on Earth.<\/p>\n
Such significant fossil and rock samples are rare and often require a bit of luck to find.<\/p>\n
Professor Ka\u00e7ar and colleagues see synthetic biology as a way to augment this important work, filling in the gaps by creating tangible reconstructions of ancient enzymes, putting them into microbes, and studying them in a modern lab.<\/p>\n
\u201cThree billion years ago is a vastly different Earth than what we see today,\u201d said University of Wisconsin-Madison Ph.D. candidate Holly Rucker.<\/p>\n
\u201cBack before the Great Oxidation Event, the atmosphere contained more carbon dioxide and methane, and life primarily consisted of anaerobic microbes.\u201d<\/p>\n
\u201cBeing able to understand how these microbes accessed a nutrient as vital as nitrogen offers a sharper picture of how life persisted and evolved in the window of time before oxygen-dependent organisms began reshaping the planet.\u201d<\/p>\n
\u201cWhile there are not fossilized enzymes we can study, these enzymes can leave behind recognizable signatures in the form of isotopes, which we can measure in rock samples.\u201d<\/p>\n
\u201cBut much of that work relied on the assumption that ancient enzymes produce the same isotopic signatures as modern versions.\u201d<\/p>\n
\u201cIt turns out, yes, at least for nitrogenase. The signatures that we see in the ancient past are the same that we see today, which then also tells us more about the enzyme itself.\u201d<\/p>\n
The authors found that even though ancient nitrogenase enzymes have different DNA sequences than modern versions, the mechanism that controls the isotopic signature preserved in the rock record has stayed the same.<\/p>\n
\u201cAs astrobiologists, we rely on understanding our planet to understand life in the Universe,\u201d Professor Ka\u00e7ar said.<\/p>\n
\u201cThe search for life starts here at home, and our home is 4 billion years old.\u201d<\/p>\n
\u201cSo, we need to understand our own past. We need to understand life before us, if we want to understand life ahead of us and life elsewhere.\u201d<\/p>\n