Study of Biogeochemical Processes Involving the Bacterium Acidithiobacillus ferrooxidans in Space Exploration

• Ano de defesa: 2023
• Autor(a) principal: Silva, Gabriel Gonçalves
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: eng
• Instituição de defesa: Biblioteca Digitais de Teses e Dissertações da USP
• Palavras-chave em Português: Acidithiobacillus ferrooxidans; Astrobiologia; Astrobiology; Biogeochemistry; Biogeoquímica; Bioleaching; Biolixiviação; Capillary electrophoresis; Eletroforese capilar; Exploração espacial; Space exploration
• Link de acesso: https://www.teses.usp.br/teses/disponiveis/46/46136/tde-28112025-111328/

To better comprehend the chances of finding or spreading life as we know it into the hostile places in the cosmos, it has become evident the need for understanding how it interacts with environments and substrates outside the Earth. This way, research in astrobiology began to show great interest in chemolithoautotrophic extremophile microorganisms, such as bacterium Acidithiobacillus ferrooxidans, which stands out for being able to use chemical reactions from inorganic species to gain the energy necessary to its metabolism, fixing inorganic carbon (such as CO2) to produce its biomass, while precipitating Fe3+-bearing minerals like Jarosite when oxidizing Fe2+. In this work, we aimed to explore the biogeochemical interactions between A. ferrooxidans and substrates like simulated iron meteorites and minerals of interest on Mars. We also offered a usage for the mineral Jarosite produced, repurposing this bioprecipitate as a substrate during space exploration. Initially, it was obtained the growing curve of the microorganism in the traditional T&K medium and the \"Standard Meteorite\" (SM) medium, mimicking the composition of iron meteorites. The growth rate constants (µ) were 0.19 h-1 and 0.21 h-1 respectively, pointing to absence of a toxic effect of Ni and Co. Meanwhile, a capillary electrophoresis methodology of quantification of Fe2+, Fe3+, Ni2+ and Co2+ was developed using 10 mmol L-1 HIBA/His and the capacitively coupled contactless conductivity detector. Then, it was demonstrated that A. ferrooxidans was able to grow obtaining its energy from the oxidation of Fe2+ that came from of Siderite (µ = 0.017 ± 0.002 h-1) and Vivianite (µ = 0.07 ± 0.03 h-1), iron-bearing minerals of interest in Martian environments. Using synthetic atmosphere, it was shown that Siderite can provide inorganic carbon to A. ferrooxidans though the CO32+ ion. In an inert atmosphere, the organism growth was obtained in a medium with Siderite, sulfur as electron donor and soluble Fe3+ as electron acceptor, a plausable condition for Mars. Finally, the bioprecipitate mineral from A. ferrooxidans growing in SM medium was tested as a soil to sustain crops for food during manned missions. While pure bioprecipitate and its mixtures with iron (simulating a metallic asteroid) and Spirulina showed to be unfeasible as a substrate to grow wheat seeds, straw and bioprecipitate mixtures (1:2 and 1:3 w/w) allowed the germination. The latter (57 ± 21 mm) had a smaller growth than the soil control (150 ± 72 mm), while the plants presented an increase of about 9 times in the Co concentration, 54 times the Fe concentration and 171 times the Ni concentration, what can cause harm to those who consume them. This way, the findings summarized here intend to contribute and expand the perspectives and possibilities of its biogeochemical interactions and the capabilities of the metabolism of A. ferrooxidans in an astrobiological context.