5:15 PM - 7:15 PM
[U12-P06] Reproduction of sustainable organic synthesis with the flow-reactor simulating ancient deep-sea alkaline hydrothermal vent
Keywords:Hydrothermal vent, Chemical evolution, Origin of life, Protometabolism, Flow-reactor, Inorganic catalyst
Organic synthesis by prebiotic metabolisms must be assumed in considering the origin of life. Deep-sea hydrothermal vents have been studied as the natural environments for such protometabolism possibly occurred. In the ancient deep sea, metal sulfides were generated by the mixing of hydrothermal fluid and seawater and could act as inorganic catalysts for prebiotic metabolic reactions like primitive enzymes. Recent studies have revealed the occurrence of power generation in deep-sea hydrothermal vents. Reducing agents in hydrothermal fluid such as H2 and H2S transfer electrons to inner surface of conductive sulfide minerals chimney wall and strong reducing power can be continuously supplied on outer surface of wall contacting seawater. The reducing power is used for sequential assimilatory organic synthetic reactions on the metal sulfides. This hypothesis has been supported by previous works in which the experiments were performed separately with step-by-step processes, such as sulfide minerals precipitation, electrical reduction of sulfide minerals, and organic reduction reactions (Kitadai et al., 2018, 2019). The next key question is whether these step reactions could possibly occur sequentially at the same place in the hydrothermal vent. In this study, we constructed a flow-reactor to reproduce the conditions of ancient hydrothermal systems and aimed to observe the sequential and sustained reactions in the flow-reactor to clarify the process of biomolecular synthesis by protometabolisms.
Sulfide ion-rich alkaline hydrothermal fluid and iron ion-rich acidic seawater were artificially prepared. In the flow reactor, the two solutions were flowed through separate lines under the control of flow rate, pressure, and temperature, and were mixed via a porous glass tube attached in the mixing unit where the two lines were connected. As a result, black particle precipitation was observed on and in the porous glass tube. Mineral composition in the sample was unclear with X-ray diffraction analysis, but elemental composition with scanning electron microscope energy dispersive X-ray spectroscopy suggested the presence of iron sulfides. Next, we flowed seawater containing glyoxylic acid and ammonia after the iron sulfide precipitation reaction in the flow-reactor, and confirmed production of glycine, which seemed to be the result of reductive amination of glyoxylic acid. The glycine production was higher when hydrogen gas was supplied to the hydrothermal fluid than when it was not supplied, suggesting the reducing power supplied from hydrogen gas. These results support the hypothesis that electrochemical reactions at deep-sea hydrothermal vents promoted protometabolisms.
Sulfide ion-rich alkaline hydrothermal fluid and iron ion-rich acidic seawater were artificially prepared. In the flow reactor, the two solutions were flowed through separate lines under the control of flow rate, pressure, and temperature, and were mixed via a porous glass tube attached in the mixing unit where the two lines were connected. As a result, black particle precipitation was observed on and in the porous glass tube. Mineral composition in the sample was unclear with X-ray diffraction analysis, but elemental composition with scanning electron microscope energy dispersive X-ray spectroscopy suggested the presence of iron sulfides. Next, we flowed seawater containing glyoxylic acid and ammonia after the iron sulfide precipitation reaction in the flow-reactor, and confirmed production of glycine, which seemed to be the result of reductive amination of glyoxylic acid. The glycine production was higher when hydrogen gas was supplied to the hydrothermal fluid than when it was not supplied, suggesting the reducing power supplied from hydrogen gas. These results support the hypothesis that electrochemical reactions at deep-sea hydrothermal vents promoted protometabolisms.