Carbon-Metal Bonds: Rare and Primordial in Metabolism.

Submarine hydrothermal vents are rich in hydrogen (H), an ancient source of electrons and chemical energy for life. Geochemical H stems from serpentinization, a process in which rock-bound iron reduces water to H. Reactions involving H and carbon dioxide (CO) in hydrothermal systems generate abiotic methane and formate; these reactions resemble the core energy metabolism of methanogens and acetogens. These organisms are strict anaerobic autotrophs that inhabit hydrothermal vents and harness energy via H-dependent CO reduction. Serpentinization also generates native metals, which can reduce CO to formate and acetate in the laboratory. The enzymes that channel H, CO, and dinitrogen (N) into methanogen and acetogen metabolism are the backbone of the most ancient metabolic pathways. Their active sites share carbon-metal bonds which, although rare in biology, are conserved relics of primordial biochemistry present at the origin of life.

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