Speaker: Dr. Terence P. Kee University of Leeds (United Kingdom)

Presentation abstract:

Abiogenesis Simulations in Far-From-Equilibrium Geo Fuel-Cell Reactors

Identifying specific processes responsible for the emergence of life and then convincingly simulating these in the laboratory are amongst the most challenging in the field of . Part of the difficulty is that plausible scenarios for the origin of life must account for both the fundamental properties of contemporary life and the geochemical conditions on the early Earth through which life arose. A primary process common to all life is the conversion of a pH gradient, established via transport (Eh), into -storing anhydride bonds (in ATP for example) via chemiosmosis across a semi- permeable membrane. Since life depends universally on pH & Eh gradients to drive , geological environments that already generate similar electrochemical energy gradients are of interest for abiogenesis. One such example includes serpentinizing systems, in which the interaction of seawater with ultramafic upper mantle rock oxidizes the ferrous iron from olivine and pyroxene in a series of exothermic reactions releasing H2 within a mineral rich, alkaline fluid (pH~10-12.5). The operations of extant life resemble those of a exchange membrane (PEM) fuel cell, where are stripped from a fuel (commonly H2) and delivered to an electron acceptor (commonly O2) after having been used to do work. Serpentinizing vents may be viewed as natural, geological fuel cells since gradients can be generated, maintained and transported across physical mineral (vent material) boundaries. As a design concept for an abiogenesis reactor, the fuel cell represents a holistic chemical system that is well understood and open to sophisticated analytical diagnostics. It is a systems approach that has not yet been exploited experimentally within the field of abiogenesis yet offers a potentially powerful theoretical and experimental model through which to explore such emergent physicochemical systems. We have constructed a geo-fuel cell simulator based on the PEM fuel cell with a view driving formation of primitive bioenergetic systems. Key to this is the ability to produce condensed phosphate (such as pyrophosphate; P2O74-; PPi) energy currency , widely regarded as primitive ancestors of ATP. We will discuss the potential for proton gradient within a geo fuel-cell to drive ATP formation within bacterial cellular extracts embedded within recognised PEM fuel cell electrolyte membranes (silica gel or Nafion polymer). We will follow this by exploring the potential for similar Pi-condensation processes mediated not via enzymatic systems but by geological processes, for example, pressure- induced Pi condensation within lamellar clay minerals controlled by proton gradients, a process postulated to be available to hydrothermal systems7 and one which could conceivable result in PPi formation.