Thiosulfate-Hydrogen Peroxide Redox Oscillator as pH Driver for Ribozyme Activity in the RNA World

Tectonically-driven oxidant production in the hot biosphere

Genomic reconstructions of the common ancestor to all life have identified genes involved in H₂O₂ and O₂ cycling. Commonly dismissed as an artefact of lateral gene transfer after oxygenic photosynthesis evolved, an alternative is a geological source of H₂O₂ and O₂ on the early Earth. Here, we show that under oxygen-free conditions high concentrations of H₂O₂ can be released from defects on crushed silicate rocks when water is added and heated to temperatures close to boiling point, but little is released at temperatures <80 °C. This temperature window overlaps the growth ranges of evolutionary ancient heat-loving and oxygen-respiring Bacteria and Archaea near the root of the Universal Tree of Life. We propose that the thermal activation of mineral surface defects during geological fault movements and associated stresses in the Earth’s crust was a source of oxidants that helped drive the (bio)geochemistry of hot fractures where life first evolved.

Researchers at Newcastle University have discovered a mechanism by which earthquakes create bursts of hydrogen peroxide and oxygen in hot underground fractures. These may have played a vital role in the early evolution and origin of life on Earth.

Modulation Effects of Permanganate and Manganese(II) Ions on the Oscillatory Dynamics in a Bromate-Sulfite Reaction System

It is important to study nonlinear dynamical systems showing pH and temperature oscillations simultaneously. Here, we systematically investigated the bromate-sulfite reaction in its coupled system. Large-amplitude temperature oscillations could be measured accompanied by the pH oscillations with or without permanganate and manganese(II) ions. The modulation effects on the oscillatory dynamics of the bromate-sulfite reaction system produced by permanganate and manganese(II) ions were investigated in detail. On the one hand, with permanganate, an additional negative pH feedback process between permanganate and bisulfite occurs, leading to weakening the pH positive feedback. The above opposite effects make the period length change unmonotonically when adjusting the permanganate concentration and flow rate. On the other hand, with Mn²⁺ as the feedback agent, the nonmonotonic change of period was not obvious because it only contained one feedback loop, which can only reinforce negative feedback without affecting positive feedback.

The Power Without the Glory: Multiple Roles of Hydrogen Peroxide in Mediating the Origin of Life

The hydrogen peroxide (HP) crucible hypothesis proposed here holds that life began in a localized environment on Earth that was perfused with a flow of hydrogen peroxide from a sustained external source, which powered and mediated molecular evolution and the protocellular RNA world. In this article, we consolidate and review recent evidence, both circumstantial and tested in simulation in our work and in the laboratory in others' work, for its multiple roles in the evolution of the first living systems: (1) it provides a periodic power source as the thiosulfate-hydrogen peroxide (THP) redox oscillator, (2) it may act as an agent of molecular change and evolution and mediator of homochirality, and (3) the THP oscillator, subject to Brownian input perturbations, produces a weighted distribution of output thermal fluctuations that favor polymerization and chemical diversification over chemical degradation and simplification. The hypothesis can help to clarify the hero and villain roles of hydrogen peroxide in cell function, and on the singularity of life: of necessity, life evolved early an armory of catalases, the continuing, and all-pervasive presence of which prevents hydrogen peroxide from accumulating anywhere in sufficient quantities to host a second origin. The HP crucible hypothesis is radical, but based on well-known chemistry and physics, it is eminently testable in the laboratory, and many of our simulations provide recipes for such experiments.

Oscillations of pH in the urea–urease system in a membrane reactor

Urea–urease reaction in an open reservoir–membrane–reactor system displays regular spontaneous oscillations of pH.

The Life Story of Hydrogen Peroxide III: Chirality and Physical Effects at the Dawn of Life

It is a remarkable observed fact that all life on Earth is homochiral, its biology using exclusively the D-enantiomer of ribose, the sugar moiety of the ribonucleic acids, and the L-enantiomers of the chiral amino acids. Motivated by concurrent work that elaborates further the role of hydrogen peroxide in providing an oscillatory drive for the RNA world (Ball & Brindley 2015a, J. R. Soc. Interface 12, 20150366, and Ball & Brindley 2015b, this journal, in press), we reappraise the structure and physical properties of this small molecule within this context. Hydrogen peroxide is the smallest, simplest molecule to exist as a pair of non-superimposable mirror images, or enantiomers, a fact which leads us to develop the hypothesis that its enantiospecific interactions with ribonucleic acids led to enantioselective outcomes. We propose a mechanism by which these chiral interactions may have led to amplification of D-ribonucleic acids and extinction of L-ribonucleic acids.

The life story of hydrogen peroxide II: a periodic pH and thermochemical drive for the RNA world

It is now accepted that primordial non-cellular RNA communities must have been subject to a periodic drive in order to replicate and prosper. We have proposed the oxidation of thiosulfate by hydrogen peroxide as this drive. This reaction system behaves as (i) a thermochemical and (ii) a pH oscillator, and in this work, we unify (i) and (ii) for the first time. We report thermally self-consistent, dynamical simulations in which the system transitions smoothly from nearly isothermal pH to fully developed thermo-pH oscillatory regimes. We use this oscillator to drive simulated replication of a 39-bp RNA species. Production of replicated duplex under thermo-pH drive was significantly enhanced compared with that under purely thermochemical drive, effectively allowing longer strands to replicate. Longer strands are fitter, with more potential to evolve enzyme activity and resist degradation. We affirm that concern over the alleged toxicity of hydrogen peroxide to life is largely misplaced in the current context, we survey its occurrence in the solar system to motivate its inclusion as a biosignature in the search for life on other worlds and highlight that pH oscillations in a spatially extended, bounded system manifest as the fundamental driving force of life: a proton gradient.