Researchers affiliated with the University of Wisconsin–Madison have successfully recreated the most ancient enzyme, which existed over 3.2 billion years ago, utilizing synthetic biology methods, and subsequently investigated its function within living microorganisms.
The findings of this research will contribute to a deeper comprehension of how life originated on Earth, while also opening new avenues for the search for potential signs of extraterrestrial life. The study’s outcomes were published in the journal Nature Communications (NatCom).
The focus of this investigation was the enzyme known as nitrogenase. This constitutes the principal biological mechanism enabling the conversion of atmospheric nitrogen into a form usable by living organisms. This entire process is fundamental to the existence of virtually the entire biosphere. The study’s authors assert that life, as we currently understand it, could not have begun without nitrogenase.
Departing from conventional methods that rely on analyzing rare geological artifacts, these specialists adopted an approach termed ancestral sequence reconstruction. Specifically, they managed to reconstruct the inferred structure of the ancient version of nitrogenase based on extant enzymes, incorporated it into bacterial genomes, and observed its performance under laboratory conditions.
This technique afforded a glimpse into an era before Earth possessed oxygen at the concentrations common today, when life primarily consisted of anaerobic microorganisms. Back then, the atmosphere was abundant in carbon dioxide and methane, making access to nitrogen a critical prerequisite for survival.
Particular scrutiny was given to what are termed isotopic signatures—the chemical traces left behind by enzymes in rock formations. Previously, scientists operated under the presumption that ancient enzymes produced the same isotopic ratios as their modern counterparts, yet direct confirmation of this supposition had remained elusive until now.
The experiments demonstrated that, despite considerable disparities in the DNA sequences between ancient and modern nitrogenase, the functional mechanism responsible for generating nitrogen isotopic signatures has remained essentially unaltered across billions of years.
These outcomes hold significance not only for elucidating Earth’s history but also for the field of astrobiology. The scientists have established a more robust benchmark for biosignatures, which future researchers can employ when searching for evidence of life on other celestial bodies.
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