From volcanic origins of chemoautotrophic life to Bacteria, Archaea and Eukarya

Abstract

The theory of a chemoautotrophic origin of life in a volcanic iron-sulphur world postulates a pioneer organism at sites of reducing volcanic exhalations. The pioneer organism is characterized by a composite structure with an inorganic substructure and an organic superstructure. Within the surfaces of the inorganic substructure iron, cobalt, nickel and other transition metal centres with sulphido, carbonyl and other ligands were catalytically active and promoted the growth of the organic superstructure through carbon fixation, driven by the reducing potential of the volcanic exhalations. This pioneer metabolism was reproductive by an autocatalytic feedback mechanism. Some organic products served as ligands for activating catalytic metal centres whence they arose. The unitary structure-function relationship of the pioneer organism later gave rise to two major strands of evolution: cellularization and emergence of the genetic machinery. This early phase of evolution ended with segregation of the domains Bacteria, Archaea and Eukarya from a rapidly evolving population of pre-cells. Thus, life started with an initial, direct, deterministic chemical mechanism of evolution giving rise to a later, indirect, stochastic, genetic mechanism of evolution and the upward evolution of life by increase of complexity is grounded ultimately in the synthetic redox chemistry of the pioneer organism.

Primary producing prokaryotic communities of brine, interface and seawater above the halocline of deep anoxic lake L'Atalante, Eastern Mediterranean Sea

“…Absence of the sunlight restricts the occurrence of photosynthesis in deep-sea, but hydrogen sulfide, ammonia and some reduced inorganic chemicals can serve as electron donors needed for the CO 2 fixation in the dark. Indeed, chemolitoautotrophs are thought to be among the first organisms that appeared on early Earth (Russell and Hall, 1997;Campbell et al, 2006;Wächtershäuser 1990Wächtershäuser , 2006Wächtershäuser , 2007.…”

Catalysis in the Primordial World

“…135 Hyperthermophiles 136 were in turn found near the underwater hydrothermal vents at Midoceanic ridges rich in dissolved hydrogen sulfide, 137,138 the possible geological habitat of pioneer organisms. 126 (Other habitats might also be magnesium-rich komatiite lava deposits 139 and hydrothermal systems developed as a consequence of asteroid impacts on early Earth, 140 but in our opinion, such events were rare.) Hyperthermophiles had possibly evolved from pioneer organisms, and were later adapted to "milder" surface conditions.…”

“…145 This provided the first (inorganic) membranes, as well as catalytic surfaces (mineral substructure). Simple molecules from volcanic liquid water phase (CO, CO 2 , COS, NH 3 , H 2 S, N 2 , H 2 , HCN) were adsorbed on a mineral substructure making an organic superstructure 126 prone to all kinds of chemical transformations. This hypothesis is supported by the finding that iron and copper sulphide minerals (pyrrhotite, pyrite, covellite, bornite, chalcopyrite, tetrahedrite) proved to be efficient catalysts in converting formamide (H 2 NCHO) into purine, adenine, and other heterocyclic bases under simulated prebiotic conditions.…”

“…Chemoautotrophic (or iron-sulphur-world) theory of life origin [124][125][126][127] rests on two assumptions. The first is that the first prebiotic catalytic reactions took place on Fe/Ni sulphide particles evolving gradually to autocatalytic systems, and ultimately to the first (pioneer) organisms.…”

Stochastic Prebiotic Chemistry within Realistic Geological Systems

“…Metabolic chemical species called "surface metabolists or surface organisms", later termed as "pioneer organism", were introduced by Günter Wächtershäuser [99][100][101][102][103][104], mainly as a challenging perspective to the prebiotic broth theory. The premise of his argument is implicitly based on simplicity preceding complexity, restricted on a two-dimensional layer.…”