Vanessa Helmbrecht

Research Interests

My research focuses on the emergence of life on early Earth and the habitability of the icy moon Enceladus. I am creating hydrothermal environments in anoxic chemical garden experiments in the lab. My study points include RNA accumulation and methanogenesis under ferruginous conditions, as well as testing, if archaea can survive and grow under Enceladus-like conditions.

Working in project: Testing the habitability of alkaline hydrothermal vents in a simulated Hadean ocean environment (DFG, 2023 - 2026)

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RNA accumulation in a ferruginous chemical garden

Mechanisms of nucleic acid accumulation were likely critical to life’s emergence in the ferruginous oceans of the early Earth. How exactly prebiotic geological settings accumulated nucleic acids from dilute aqueous solutions, is poorly understood. As a possible solution to this concentration problem, we simulated the conditions of prebiotic low-temperature alkaline hydrothermal vents in co-precipitation experiments to investigate the potential of ferruginous chemical gardens to accumulate nucleic acids via sorption. Our findings reveal that in the oceans of the early Earth, white and green rust chimneys were likely key geochemical features that can rapidly sequester and accumulate RNA. This represents a new mechanism for nucleic acid accumulation, in addition to wet dry cycles, and may have promoted RNA survival in a dilute prebiotic ocean.

Helmbrecht, V., Weingart, M., Klein, F., Braun, D., & Orsi, W. D. (2023). White and green rust chimneys accumulate RNA in a ferruginous chemical garden. Geobiology, 21(6), 758-769.

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Methanogenesis in a prebiotic iron-sulfide environment

Molecular hydrogen is the electron donor for the ancient exergonic reductive acetyl-coenzyme A pathway (acetyl-CoA pathway), which is used by hydrogenotrophic methanogenic archaea. How the presence of iron-sulfides influenced the acetyl-CoA pathway under primordial early Earth geochemistry is still poorly understood. Here, we show that the iron-sulfides mackinawite (FeS) and greigite (Fe3S4), which formed in chemical garden experiments, produce abiotic H2 in sufficient quantities to support hydrogenotrophic growth of the hyperthermophilic methanogen Methanocaldococcus jannaschii. Abiotic H2 from iron-sulfide formation promoted CO2-fixation and methanogenesis and induced overexpression of genes encoding the acetyl-CoA pathway. We demonstrate that H2 from iron-sulfide precipitation under simulated early Earth conditions fuels a H2-dependent primordial metabolism.

Helmbrecht, V., Reichelt, R., Grohmann, D., & Orsi, W. D. (2025). Simulated early Earth geochemistry fuels a hydrogen-dependent primordial metabolism. Nature Ecology & Evolution, 1-10.

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Is cellular life possible on the icy moon Enceladus?

Enceladus, one of Saturn’s icy moons, is considered a prime candidate in the search for extraterrestrial life because it harbors a global subsurface ocean and a rocky core beneath its thick ice shell. Observations from the Cassini spacecraft revealed plumes of water vapor, organic molecules, and molecular hydrogen (H2) venting from cracks near its south pole, indicating hydrothermal activity on the seafloor. These hydrothermal vents could provide chemical energy, similar to Earth’s hydrothermal vents. The detection of hydrogen is especially promising to fuel microbial life. We investigate abiotic H2 formation in simulated Enceladus-like experiments, containing the methanogenic archaeon Methanothermococcus okinawensis. We analyze their methane (CH4) production, their growth and their gene expression under ice moon conditions.

Publications