Iron-sulfur world theory
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The iron-sulfur world theory is a hypothesis for the origin of life advanced by Günter Wächtershäuser involving forms of iron and sulfur. Wächtershäuser claims that an early form of metabolism predated genetics. Metabolism here means a cycle of chemical reactions that produce energy in a form that can be harnessed by other processes. The idea is that once a primitive metabolic cycle was established, it began to produce ever more complex compounds.
A key idea of the theory is that this early chemistry of life occurred not in bulk solution in the oceans, but on mineral surfaces (e.g. iron pyrites) near deep submarine vents. The first 'cells' would have been lipid bubbles on the mineral surfaces.
Wächtershäuser has hypothesized a special role for acetic acid, a simple combination of carbon, hydrogen, and oxygen found in vinegar. Acetic acid is part of the citric acid cycle that is fundamental to metabolism in cells.
Some of the fundamental ideas can be summarized in the following brief recipe for life:
- "Boil water. Stir in iron sulfide and nickel sulfide. Bubble in carbon monoxide and rotten egg gas. Wait for peptides to form."
More technically, Wächtershäuser hypothesized the following steps for producing proteins:
- Produce acetic acid through metallic ion catalysis.
- Add carbon to the acetic acid molecule to produce three-carbon pyruvic acid.
- Add ammonia to form amino acids.
- Produce peptides and then proteins.
Both acetic acid and pyruvic acid are key chemicals in the citric acid cycle.
In 1997, Wächtershäuser and Claudia Huber mixed carbon monoxide, hydrogen sulfide, nickel sulfide, and iron sulfide particles at 100°C and demonstrated that amino acids could form. The following year, using the same ingredients, they were able to produce peptides.