Computational Models of Polymer Synthesis Driven by Dehydration/Rehydration Cycles: Repurination in Simulated Hydrothermal Fields

Hargrave, Mason; Thompson, Spencer K.; Deamer, David W.

doi:10.1007/s00239-018-9865-5

Cited by 9 publications

(8 citation statements)

References 13 publications

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“…However, a single cycle might lead to a few oligomers, but these would begin to undergo hydrolysis upon rehydration. We propose that not just a single cycle but instead continuous wet-dry cycles would allow polymers to exist in a steady state and grow more complex as solutes in a prebiotic warm little pond (Hargrave et al, 2018). As long as the rate of synthesis exceeds the rate of hydrolysis, multiple cycles operating in conjunction with a kinetic trap will inevitably HOT SPRING ORIGIN OF LIFE produce an accumulation of polymers (Higgs, 2016).…”

Section: Damer and Deamermentioning

confidence: 99%

The Hot Spring Hypothesis for an Origin of Life

2020

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We present a testable hypothesis related to an origin of life on land in which fluctuating volcanic hot spring pools play a central role. The hypothesis is based on experimental evidence that lipid-encapsulated polymers can be synthesized by cycles of hydration and dehydration to form protocells. Drawing on metaphors from the bootstrapping of a simple computer operating system, we show how protocells cycling through wet, dry, and moist phases will subject polymers to combinatorial selection and draw structural and catalytic functions out of initially random sequences, including structural stabilization, pore formation, and primitive metabolic activity. We propose that protocells aggregating into a hydrogel in the intermediate moist phase of wet-dry cycles represent a primitive progenote system. Progenote populations can undergo selection and distribution, construct niches in new environments, and enable a sharing network effect that can collectively evolve them into the first microbial communities. Laboratory and field experiments testing the first steps of the scenario are summarized. The scenario is then placed in a geological setting on the early Earth to suggest a plausible pathway from life's origin in chemically optimal freshwater hot spring pools to the emergence of microbial communities tolerant to more extreme conditions in dilute lakes and salty conditions in marine environments. A continuity is observed for biogenesis beginning with simple protocell aggregates, through the transitional form of the progenote, to robust microbial mats that leave the fossil imprints of stromatolites so representative in the rock record. A roadmap to future testing of the hypothesis is presented. We compare the oceanic vent with land-based pool scenarios for an origin of life and explore their implications for subsequent evolution to multicellular life such as plants. We conclude by utilizing the hypothesis to posit where life might also have emerged in habitats such as Mars or Saturn's icy moon Enceladus. Key Words: Origin of life-Prebiotic chemistry-Hydrothermal systems-Protocells-Progenotes-Microbial communities. Astrobiology 20, 429-452. ''To postulate one fortuitously catalyzed reaction, perhaps catalyzed by a metal ion, might be reasonable, but to postulate a suite of them is to appeal to magic.''

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Section: Damer and Deamermentioning

confidence: 99%

The Hot Spring Hypothesis for an Origin of Life

2020

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“…Although wet-dry cycling has been around since at least the nineteen seventies as a proposed prebiotic mechanism for polymerizing amino acids [ 9 , 12 , 13 , 14 ], a similar struggle but with RNA led to the re-opening of Darwin’s casket for the resurrection of “pond theory” [ 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 ]. However, that casket was empty!…”

Section: Evaporating Pond Theory Of Life’s “Origin”mentioning

confidence: 99%

The “Water Problem”(sic), the Illusory Pond and Life’s Submarine Emergence—A Review

Russell

2021

Life

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The assumption that there was a “water problem” at the emergence of life—that the Hadean Ocean was simply too wet and salty for life to have emerged in it—is here subjected to geological and experimental “reality checks”. The “warm little pond” that would take the place of the submarine alkaline vent theory (AVT), as recently extolled in the journal Nature, flies in the face of decades of geological, microbiological and evolutionary research and reasoning. To the present author, the evidence refuting the warm little pond scheme is overwhelming given the facts that (i) the early Earth was a water world, (ii) its all-enveloping ocean was never less than 4 km deep, (iii) there were no figurative “Icelands” or “Hawaiis”, nor even an “Ontong Java” then because (iv) the solidifying magma ocean beneath was still too mushy to support such salient loadings on the oceanic crust. In place of the supposed warm little pond, we offer a well-protected mineral mound precipitated at a submarine alkaline vent as life’s womb: in place of lipid membranes, we suggest peptides; we replace poisonous cyanide with ammonium and hydrazine; instead of deleterious radiation we have the appropriate life-giving redox and pH disequilibria; and in place of messy chemistry we offer the potential for life’s emergence from the simplest of geochemically available molecules and ions focused at a submarine alkaline vent in the Hadean—specifically within the nano-confined flexible and redox active interlayer walls of the mixed-valent double layer oxyhydroxide mineral, fougerite/green rust comprising much of that mound.

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“…The loss of nucleobase, as described by Bapat et al and Mungi et al, may account at least partially for the low yield of replication observed in the previous studies. Further description of the abiotic nucleotide polymerization in the presence of lipids came from a theoretical paper by Hargreaves et al whose computational model described qualitatively the evolution of reagents (monomers) and products (polymers) undergoing DH-RH cycling in hydrothermal pools [33]. The results obtained by these authors showed that dehydration synthesis of RNA polymers from ribonucleotides, in combination with the hydrolysis of RNA polymers back into ribonucleotides, produced a steady state yield of RNA polymers.…”

Section: Transfer Of Informationmentioning

confidence: 99%

Lipid-Assisted Polymerization of Nucleotides

Olasagasti

Rajamani

2019

Life

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In addition to being one of the proponents of the “Lipid World hypothesis”, David Deamer, together with other colleagues, pioneered studies involving formation of RNA-like oligomers from their ‘non-activated’, prebiotically plausible monomeric moieties. In particular, the pioneering work in this regard was a publication from 2008 in Origins of Life and Evolution of Biospheres, The Journal of the International Astrobiology Society, wherein we described the formation of RNA-like oligomers from nucleoside 5’-monophosphates. In that study, we had simulated a terrestrial geothermal environment, a niche that is thought to have facilitated the prebiotic non-enzymatic synthesis of polynucleotides. We showed that a mixture of lipids and non-activated mononucleotides resulted in the formation of relatively long strands of RNA-like polymers when subjected to repeated cycles of dehydration and rehydration (DH-RH). Since 2008, terrestrial geothermal niches and DH-RH conditions have been explored in the context of several other prebiotic processes. In this article, we review the work that we and other researchers have carried out since then in this line of research, including the development of new apparatus to carry out the simulation of prebiotic terrestrial geothermal environments.

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Computational Models of Polymer Synthesis Driven by Dehydration/Rehydration Cycles: Repurination in Simulated Hydrothermal Fields

Cited by 9 publications

References 13 publications

The Hot Spring Hypothesis for an Origin of Life

The Hot Spring Hypothesis for an Origin of Life

The “Water Problem”(sic), the Illusory Pond and Life’s Submarine Emergence—A Review

Lipid-Assisted Polymerization of Nucleotides

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