Robust, exponential accumulation of nucleotides driven entirely by thermal gradient was observed in simulated hydrothermal pores
Baaske P,Weinert FM,Duhr S,Lemke KH,Russell MJ,Braun D
We simulate molecular transport in elongated hydrothermal pore systems influenced by a thermal gradient. We find extreme accumulation of molecules in a wide variety of plugged pores. The mechanism is able to provide highly concentrated single nucleotides, suitable for operations of an RNA world at the origin of life. It is driven solely by the thermal gradient across a pore. On the one hand, the fluid is shuttled by thermal convection along the pore, whereas on the other hand, the molecules drift across the pore, driven by thermodiffusion. As a result, millimeter-sized pores accumulate even single nucleotides more than 10(8)-fold into micrometer-sized regions. The enhanced concentration of molecules is found in the bulk water near the closed bottom end of the pore. Because the accumulation depends exponentially on the pore length and temperature difference, it is considerably robust with respect to changes in the cleft geometry and the molecular dimensions. Whereas thin pores can concentrate only long polynucleotides, thicker pores accumulate short and long polynucleotides equally well and allow various molecular compositions. This setting also provides a temperature oscillation, shown previously to exponentially replicate DNA in the protein-assisted PCR. Our results indicate that, for life to evolve, complicated active membrane transport is not required for the initial steps. We find that interlinked mineral pores in a thermal gradient provide a compelling high-concentration starting point for the molecular evolution of life.
eHydrothermal vents and environments are sites for origin and evolution of life.
Hydrothermal vents and environments are sites for origin and evolution of life.
Archean hydrothermal systems related to origin and evolution of life can be tested in present-day hydrothermal systems.
John A. Baross, Sarah E. Hoffman.
Submarine hydrothermal vents are the only comtemporary geological environment which may be called truly primeval; they continue to be a major source of gases and dissolved elements to the modern ocean as they were to the Archean ocean. Then, as now, they encompassed a multiplicity of physical and chemical gradients as a direct result of interactions between extensive hydrothermal activity in the Earth's crust and the overlying oceanic and atmospheric environments. We have proposed that these gradients provided the necessary multiple pathways for the abiotic synthesis of chemical compounds, origin and evolution of "precetls' and 'precell' communities and, ultimately, the evolution of free-living organisms. This hypothesis is consistent with the tectonic, paleontological, and degassing history of the earth and with the use of thermal energy sources in the laboratory to synthesize amino acids and complex organic compounds. In this paper, we expand upon the geophysical, chemical, and possible microbiological analogies between contemporary and Archean hydrothermal systems and suggest several hypotheses, related to our model for the origin and evolution of life at Archean vents, which can be tested in present-day hydrothermal systems.
eHydrothermal systems located at plates viable environments for chemical evolution and orgin of life.
Hydrothermal systems located at plates viable environments for chemical evolution and orgin of life.
Hydrothermal systems are where primitive life would have been protected against meteorite impacts and vaporization of the ocean. Supercritical fluids are solvents of organic compounds and of potential for the chemical reactions for the origin of life.
Nils G. Holm
The paradigm change in geology by the general acceptance of plate tectonics around two decades aga has brought about an increased interest in geothermal processes at plate boundaries. Thus the enhanced research activity at spreading centers led to the discovery of large spectacular submarine hydrothermal systems of global significance to ocean chemistry and geochemistry. Among the best known such areas are the Galapagos Ridge (Corliss et al., 1979), the East Pacific Rise at 21°N (Francheteau et al., 1979; Spiess et al., 1980), and the Juan de Fuca Ridge (Chase et al., 1985). Rona and coworkers (1983) have compiled the early landmark studies of hydrothermal processes at seafloor spreading centers. Recently Edmond (1991) also reviewed U.S. research on oceanic hydrothermal chemistry for the period 1987-1990. The spectacular nature of marine hydrothermal systems with features such as ‘black smokers’, ‘white smokers’ and peculiar ecosystems that are independent of sunlight as a source of reducing power has focused much interest on hydrothermal processes for the explanation of an array of geochemical processes and phenomena. Hydrothermal systems located at global plate spreading centers soon attracted the attention of geochemists as viable environments for chemical evolution and the origin of life (cf. Ingmanson and Dowler, 1981).
Hydrothermal vents provide a sustained source of chemical energy by virtue of the H2/CO2 chemical potential.
Martin W,Russell MJ
A model for the origin of biochemistry at an alkaline hydrothermal vent has been developed that focuses on the acetyl-CoA (Wood-Ljungdahl) pathway of CO2 fixation and central intermediary metabolism leading to the synthesis of the constituents of purines and pyrimidines. The idea that acetogenesis and methanogenesis were the ancestral forms of energy metabolism among the first free-living eubacteria and archaebacteria, respectively, stands in the foreground. The synthesis of formyl pterins, which are essential intermediates of the Wood-Ljungdahl pathway and purine biosynthesis, is found to confront early metabolic systems with steep bioenergetic demands that would appear to link some, but not all, steps of CO2 reduction to geochemical processes in or on the Earth's crust. Inorganically catalysed prebiotic analogues of the core biochemical reactions involved in pterin-dependent methyl synthesis of the modern acetyl-CoA pathway are considered. The following compounds appear as probable candidates for central involvement in prebiotic chemistry: metal sulphides, formate, carbon monoxide, methyl sulphide, acetate, formyl phosphate, carboxy phosphate, carbamate, carbamoyl phosphate, acetyl thioesters, acetyl phosphate, possibly carbonyl sulphide and eventually pterins. Carbon might have entered early metabolism via reactions hardly different from those in the modern Wood-Ljungdahl pathway, the pyruvate synthase reaction and the incomplete reverse citric acid cycle. The key energy-rich intermediates were perhaps acetyl thioesters, with acetyl phosphate possibly serving as the universal metabolic energy currency prior to the origin of genes. Nitrogen might have entered metabolism as geochemical NH3 via two routes: the synthesis of carbamoyl phosphate and reductive transaminations of alpha-keto acids. Together with intermediates of methyl synthesis, these two routes of nitrogen assimilation would directly supply all intermediates of modern purine and pyrimidine biosynthesis. Thermodynamic considerations related to formyl pterin synthesis suggest that the ability to harness a naturally pre-existing proton gradient at the vent-ocean interface via an ATPase is older than the ability to generate a proton gradient with chemistry that is specified by genes.