Marine phosphate availability and the chemical origins of life on Earth

Abstract

Prebiotic systems chemistry suggests that high phosphate concentrations were necessary to synthesise molecular building blocks and sustain primitive cellular systems. However, current understanding of mineral solubility predicts negligible phosphate concentrations for most natural waters, yet the role of Fe2+, ubiquitous on early Earth, is poorly quantified. Here we determine the solubility of Fe(II)-phosphate in synthetic seawater as a function of pH and ionic strength, integrate these observations into a thermodynamic model that predicts phosphate concentrations across a range of aquatic conditions, and validate these predictions against modern anoxic sediment pore waters. Experiments and models show that Fe2+ significantly increases the solubility of all phosphate minerals in anoxic systems, suggesting that Hadean and Archean seawater featured phosphate concentrations ~103–104 times higher than currently estimated. This suggests that seawater readily met the phosphorus requirements of emergent cellular systems and early microbial life, perhaps fueling primary production during the advent of oxygenic photosynthesis.

Prebiotic triose glycolysis promoted by co-catalytic proline and phosphate in neutral water

“…Geochemical models suggest high concentrations of P i (>1 M) would accumulate coincidently with high concentrations of carbonate in natural (prebiotic) environments. 21 Interestingly, we observe carbonate has no detrimental effect on the observed Pro /P i catalysed aldol (ESI,† Fig. S39 and S40).…”

Nanoparticulate apatite and greenalite in oldest, well-preserved hydrothermal vent precipitates

“…A final consideration affecting the estimates of total seawater P concentrations relates to the presence of dissolved Fe(II), which is demonstrated by the occurrence of greenalite and siderite in the jaspilites. Brady et al ( 64 ), on the basis of new and existing solubility data for the Fe-phosphate system in seawater, showed that dissolved Fe(II) leads to strong aqueous complexing with dissolved phosphate species, in turn, increasing the solubility of all phosphate minerals. Accounting for this effect leads to even higher estimates for seawater P concentrations, which, for 10-nm FAP particles, corresponds to 10 to 60 μmol/kg (at pH 7) to 40 to 150 μmol/kg (at pH 6.5) (Fig.…”

A single phosphorylation mechanism in early metabolism – the case of phosphoenolpyruvate

“…Third, phosphate is geochemically more widely available than simple organic thiols. 61–64 Furthermore, whereas acyl phosphates do not contain sulfur, thiol-based leaving groups in metabolism, such as CoA, generally contain phosphoryl groups. Fourth, in water, the formation of acyl phosphates from carboxylates is arguably chemically simpler than the conversion of carboxylates to thioesters – the former requires only a single component (an activated phosphate), whereas the latter requires two (a thiol and an activating agent for the carboxylate).…”