Autotrophic Origin Of Life Research Articles

Cover Feature: Electrochemistry at Deep‐Sea Hydrothermal Vents: Utilization of the Thermodynamic Driving Force towards the Autotrophic Origin of Life (ChemElectroChem 5/2019)

Cover Feature: Electrochemistry at Deep‐Sea Hydrothermal Vents: Utilization of the Thermodynamic Driving Force towards the Autotrophic Origin of Life (ChemElectroChem 5/2019)

Electrochemistry at Deep‐Sea Hydrothermal Vents: Utilization of the Thermodynamic Driving Force towards the Autotrophic Origin of Life

AbstractTemperature gradients are an under‐utilized source of energy with which to drive chemical reactions. Here, we review our past efforts to understand how deep‐sea hydrothermal vents may harness thermal energy to promote difficult chemical reactions such as CO2 reduction. Strategies to amplify the driving force using temperature will be covered first, followed by a discussion on how spatially separated thermodynamic gradients can be used to regulate reaction selectivity. Although desirable material properties of hydrothermal vent walls have been inferred previously from the bioenergetic membranes of modern cells, strategies based on fundamental laws of physical chemistry allow naturally occurring chimney minerals to circumvent the lack of structural and catalytic optimization. The principles that underlie both the establishment and the utilization of the thermodynamic driving force at hydrothermal vents can be employed in abiotic systems such as the modern chemical industry, yielding insight into carbon fixation reactions important today and possibly at the autotrophic origin of life.

Analysis Suggests Habitat, Lifestyle for Last Universal Common Ancestor

The last universal common ancestor (LUCA) apparently was a thermophilic, anaerobic, nitrogen-fixing microorganism, according to William F. Martin from the Institute of Molecular Evolution at Heinrich Heine University Dusseldorf, in Dusseldorf, Germany, and his collaborators. Their findings support the theory of an autotrophic origin of life involving the Wood–Ljungdahl pathway in a hydrothermal setting. Details appeared July 25, 2016 in Nature Microbiology (doi:10.1038/nmicrobiol.2016.116).

The stereochemical basis of the genetic code and the (mostly) autotrophic origin of life.

Spark-tube experiments and analysis of meteorite contents have led to the widespread notion that abiotic organic molecules were the first life components. However, there is a contradiction between the abundance of simple molecules, such as the amino acids glycine and alanine, observed in these studies, and the minimal functional complexity that even the least sophisticated living system should require. I will argue that although simple abiotic molecules must have primed proto-metabolic pathways, only Darwinian evolving systems could have generated life. This condition may have been initially fulfilled by both replicating RNAs and autocatalytic reaction chains, such as the reductive citric acid cycle. The interactions between nucleotides and biotic amino acids, which conferred new functionalities to the former, also resulted in the progressive stereochemical recognition of the latter by cognate anticodons. At this point only large enough amino acids would be recognized by the primordial RNA adaptors and could polymerize forming the first peptides. The gene duplication of RNA adaptors was a crucial event. By removing one of the anticodons from the acceptor stem the new RNA adaptor liberated itself from the stereochemical constraint and could be acylated by smaller amino acids. The emergence of messenger RNA and codon capture followed.

A phylogenetic approach to the early evolution of autotrophy: the case of the reverse TCA and the reductive acetyl-CoA pathways.

In recent decades, a number of hypotheses on the autotrophic origin of life have been presented. These proposals invoke the emergence of reaction networks leading from CO or CO₂ to the organic molecules required for life. It has also been suggested that the last (universal) common ancestor (LCA or LUCA) of all extant cell lineages was a chemolitho-autotrophic thermophilic anaerobe. The antiquity of some carbon fixation pathways, the phylogenetic basal distribution of some autotrophic organisms, and the catalytic properties of iron-sulfur minerals have been advanced in support of these ideas. Here we critically examine the phylogenetic distribution and evolution of enzymes that are essential for two of the most ancient autotrophic means of metabolism: the reductive tricarboxylic acid (rTCA) cycle and the reductive acetyl-CoA pathway. Phylogenetic analysis of citryl-CoA synthetase and of citryl-CoA lyase, key enzymatic components of the rTCA cycle, and of CO dehydrogenase/acetyl-CoA synthase, a key enzyme in the reductive acetyl-CoA pathway, revealed that all three enzymes have undergone major lateral transfer events and therefore cannot be used as proof of the LCA's metabolic abilities nor as evidence of an autotrophic origin of life.

Metalloproteins and the pyrite-based origin of life: a critical assessment.

We critically examine the proposal by Wächtershäuser (Prokaryotes 1:275-283, 2006a, Philos Trans R Soc Lond B Biol Sci 361: 787-1808, 2006b) that putative transition metal binding sites in protein components of the translation machinery of hyperthermophiles provide evidence of a direct relationship with the FeS clusters of pyrite and thus indicate an autotrophic origin of life in volcanic environments. Analysis of completely sequenced cellular genomes of Bacteria, Archaea and Eucarya does not support the suggestion by Wächtershäuser (Prokaryotes 1:275-283, 2006a, Philos Trans R Soc Lond B Biol Sci 361: 787-1808, 2006b) that aminoacyl-tRNA synthetases and ribosomal proteins bear sequence signatures typical of strong covalent metal bonding whose absence in mesophilic species reveals a process of adaptation towards less extreme environments.

Primordial amino acids by reductive amination of α-oxo acids in conjunction with the oxidative formation of pyrite

Abstract The theory of an autotrophic origin of life postulates a primordial formation of amino acids by a mild and specific chemical energy source, namely by the reductive amination of α-oxo acids in conjunction with the oxidative formation of pyrite. Here we show experimental proof for this reaction, which involves carbon dioxide as catalyst.