A Possible Primordial Acetyleno/Carboxydotrophic Core Metabolism

Abstract

Carbon fixation, in addition to the evolution of metabolism, is a main requirement for the evolution of life. Here, we report a one-pot carbon fixation of acetylene (C2H2) and carbon monoxide (CO) by aqueous nickel sulfide (NiS) under hydrothermal (>100 °C) conditions. A slurry of precipitated NiS converts acetylene and carbon monoxide into a set of C2–4-products that are surprisingly representative for C2–4-segments of all four central CO2-fixation cycles of the domains Bacteria and Archaea, whereby some of the products engage in the same interconversions, as seen in the central CO2-fixation cycles. The results suggest a primordial, chemically predetermined, non-cyclic acetyleno/carboxydotrophic core metabolism. This metabolism is based on aqueous organo–metal chemistry, from which the extant central CO2-fixation cycles based on thioester chemistry would have evolved by piecemeal modifications.

Formation of Thiophene under Simulated Volcanic Hydrothermal Conditions on Earth—Implications for Early Life on Extraterrestrial Planets?

“…In earlier work starting from acetylene, CO or cyanide under simulated hydrothermal conditions, we showed that nickel, especially NiS, is a potent catalyst for the formation of organic molecules, such as fatty acids, intermediates serving in biological carbon fixation and amino acids [ 11 , 12 , 28 ]. As we can now show, NiS catalyzes additionally the formation of thiophene from acetylene.…”

“…We have shown earlier that acetylene is also an excellent source for primordial carbon fixation, especially in combination with carbon monoxide, e.g., for the synthesis of short chain fatty acids [ 11 ] and intermediates of extant carbon fixation cycles [ 12 ]. On Earth, acetylene is present in fumarolic exhalations [ 13 ].…”

“…Based on this hypothesis, we here report the facile abiotic formation of thiophene and some of its derivatives from acetylene and metallo-sulfides, especially NiS, under aqueous conditions at 105 °C. In context with the formation of potential building units and reaction networks for the emergence of metabolism under the same conditions [ 11 , 12 ] and capitalizing on recent hypotheses [ 2 ], the detection of extraterrestrial or terrestrial thiophenes could therefore indeed be indicative of early metabolic evolution under chemoautotrophic conditions.…”

Reciprocally-coupled Gating: Strange Loops in Bioenergetics, Genetics, and Catalysis

“…Reflexive in this context simply refers to a closure property in which the product of the final catalyst provides the substrate for the first. The relevance of these control networks is almost certainly validated by their homologies to various chemical cycles, such as the formose cycle [31], the Krebs cycle [32], and related core metabolisms [33]. The more recent studies strengthen arguments favoring metabolism first, autotrophic pre-biology forms.…”

Reciprocally-Coupled Gating: Strange Loops in Bioenergetics, Genetics, and Catalysis

“…That afforded a means to systematize the bewildering array of networks for modeling the emergence of life-like properties built by computational theorists as "Reflexive Autocatalytic Food Sets" (RAFS [27][28][29][30][31][32][33]) or GARDs [34], and show that they have the same formal structure [19]. The relevance of these control networks is almost certainly validated by their homologies to various chemical cycles, such as the formose cycle [35], the Krebs cycle [36], and related core metabolisms [37]. More recent studies strengthen arguments favoring metabolism first, autotrophic pre-biology forms.…”