Alpha-Oxo Acids Assisted Transformation of FeS to Fe3S4 at Low Temperature: Implications for Abiotic, Biotic, and Prebiotic Mineralization

摘要

The mineral greigite (Fe3S4) distributes widely in anoxic marine and lake sedimentary systems, with important implications for magnetostratigraphy and paleomagnetism. In living organisms, magnetotactic bacteria can synthesize greigite grains with regular sizes and morphologies. The cubic Fe3S4 structure also occurs as an integral constituent and active center in a family of iron-sulfur proteins in all life-forms on Earth. This basic biochemistry shared by all organisms implies that the Fe3S4 structure might have evolved in the first protocell. Therefore, greigite is of general interest in geochemistry, geophysics, biomineralogy, and origin-of-life sciences. However, the growth of thermodynamically metastable Fe3S4 crystals often requires strictly defined conditions because both Fe and S show variable valences and it is hard to tune their valence fluctuation. Here, we show that freshly precipitated FeS can be selectively oxidized to form greigite in the presence of -oxo acids, even at room temperature. Based on a brief overview of the experimental findings, a metal-organic complex intermediate model has been put forward and discussed for the discriminative chemical transformation. The results not only provide a possible pathway for the abiotic formation of greigite in nature but also may help explain the biotic mineralization of greigite in magnetotactic bacteria. Moreover, in the context of prebiotic evolution, along with the synergic evolution between greigite and -oxo acids, Fe3S4 might have been sequestered by primordial peptides, and the whole finally evolved into the first iron-sulfur protein.