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A study on the geochemical conditions in hydrothermal vents
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Resumo(s)
Alkaline hydrothermal vents are ancient ocean structures, H2-producing, with pH, temperature and redox gradients which promote reduction and have been of great interest for Origin of Life researchers10,23,24. In the laboratory, CO2 can be reduced under hydrothermal conditions to organic molecules, such as ethanol, formate, methane, acetate and pyruvate 255,6. These molecules are also part of the ancient acetyl-CoA pathway, an exergonic, H2-dependent, CO2 reducing metabolic pathway, which possibly dates back to the Last Universal Common Ancestor (LUCA)3,26. In addition, the minerals within alkaline hydrothermal vents are rich in iron and nickel, two metals that are commonly found in the catalytic centers of modern-day enzymes, including the acetyl-CoA pathway27. They were also essential to catalyze CO2 reduction to synthesize more complex molecules such as pyruvate in the laboratory28,29. The idea that alkaline hydrothermal vents can be associated to an ancient metabolic pathway leads to an interesting argument for the location of the origin of metabolism. In this work I looked to expand the range of studies with hydrothermal conditions to new topics beyond CO2 reduction, exploring the effects of the complex microporous structure of these vents and if such rudimentary conditions could support modern day coenzymes and its redox reactions. For the first study an open microporous framework with zeolite and Laponite-RD was developed to simulate the vents’ structure and reproduced previous CO2 reduction experiments in this new setting. Secondly, the stability and reduction of nicotinamide adenine dinucleotide (NAD) under hydrothermal conditions was studied, an ancient coenzyme essential for metabolism.Results suggest that the framework used promotes the synthesis of more complex molecules such as pyruvate and acetate, in detriment of the production of simpler ones such as formate and that NAD is not only stable in alkaline fluids, but also can be reduced in the presence magnetite (Fe3O4). Reducing contamination and improving analytic methods are important next steps to take for this work, which already presents an avenue that further connects alkaline hydrothermal vents to the origin of metabolism.
Descrição
Tese de mestrado, Biologia Molecular e Genética, Universidade de Lisboa, Faculdade de Ciências, 2020
Palavras-chave
Fontes hidrotermais estrutura microporosa origem do metabolismo redução magnetite Teses de mestrado - 2020