scholarly journals Beating the acetyl coenzyme A-pathway to the origin of life

2013 ◽  
Vol 368 (1622) ◽  
pp. 20120258 ◽  
Author(s):  
Wolfgang Nitschke ◽  
Michael J. Russell
Keyword(s):  
Phylogenetic Analysis ◽  
Boundary Conditions ◽  
Origin Of Life ◽  
Carbon Metabolism ◽  
Acetyl Coenzyme A ◽  
The Past ◽  
Proposed Model ◽  
The Origin Of Life ◽  
To Come ◽  
Present Understanding

Attempts to draft plausible scenarios for the origin of life have in the past mainly built upon palaeogeochemical boundary conditions while, as detailed in a companion article in this issue, frequently neglecting to comply with fundamental thermodynamic laws. Even if demands from both palaeogeochemistry and thermodynamics are respected, then a plethora of strongly differing models are still conceivable. Although we have no guarantee that life at its origin necessarily resembled biology in extant organisms, we consider that the only empirical way to deduce how life may have emerged is by taking the stance of assuming continuity of biology from its inception to the present day. Building upon this conviction, we have assessed extant types of energy and carbon metabolism for their appropriateness to conditions probably pertaining in those settings of the Hadean planet that fulfil the thermodynamic requirements for life to come into being. Wood–Ljungdahl (WL) pathways leading to acetyl CoA formation are excellent candidates for such primordial metabolism. Based on a review of our present understanding of the biochemistry and biophysics of acetogenic, methanogenic and methanotrophic pathways and on a phylogenetic analysis of involved enzymes, we propose that a variant of modern methanotrophy is more likely than traditional WL systems to date back to the origin of life. The proposed model furthermore better fits basic thermodynamic demands and palaeogeochemical conditions suggested by recent results from extant alkaline hydrothermal seeps.

scholarly journals Environmental boundary conditions for the origin of life converge to an organo-sulfur metabolism

2019 ◽  
Vol 3 (12) ◽  
pp. 1715-1724 ◽  
Author(s):  
Joshua E. Goldford ◽  
Hyman Hartman ◽  
Robert Marsland ◽  
Daniel Segrè
Keyword(s):  
Boundary Conditions ◽  
Origin Of Life ◽  
Sulfur Metabolism ◽  
The Origin Of Life

Understanding Life: A Bioinformatics Perspective

2016 ◽  
Vol 25 (2) ◽  
pp. 231-245 ◽  
Author(s):  
Natalia Szostak ◽  
Szymon Wasik ◽  
Jacek Blazewicz
Keyword(s):  
Origin Of Life ◽  
Rna World ◽  
Origins Of Life ◽  
Life Itself ◽  
Wet Lab ◽  
The Origin Of Life ◽  
To Come ◽  
World Hypothesis ◽  
Definition Of ◽  
Rna World Hypothesis

According to some hypotheses, from a statistical perspective the origin of life seems to be a highly improbable event. Although there is no rigid definition of life itself, life as it is, is a fact. One of the most recognized hypotheses for the origins of life is the RNA world hypothesis. Laboratory experiments have been conducted to prove some assumptions of the RNA world hypothesis. However, despite some success in the ‘wet-lab’, we are still far from a complete explanation. Bioinformatics, supported by biomathematics, appears to provide the perfect tools to model and test various scenarios of the origins of life where wet-lab experiments cannot reflect the true complexity of the problem. Bioinformatics simulations of early pre-living systems may give us clues to the mechanisms of evolution. Whether or not this approach succeeds is still an open question. However, it seems likely that linking efforts and knowledge from the various fields of science into a holistic bioinformatics perspective offers the opportunity to come one step closer to a solution to the question of the origin of life, which is one of the greatest mysteries of humankind. This paper illustrates some recent advancements in this area and points out possible directions for further research.

The Tempo and mode(S) of Prebiotic Evolution

1997 ◽  
Vol 161 ◽  
pp. 419-429 ◽  
Author(s):  
Antonio Lazcano
Keyword(s):  
Origin Of Life ◽  
Organic Compounds ◽  
Biological Evolution ◽  
Current Evidence ◽  
Early Diversification ◽  
Time Period ◽  
The Galaxy ◽  
History Of ◽  
Widespread Phenomenon ◽  
The Origin Of Life

AbstractDifferent current ideas on the origin of life are critically examined. Comparison of the now fashionable FeS/H2S pyrite-based autotrophic theory of the origin of life with the heterotrophic viewpoint suggest that the later is still the most fertile explanation for the emergence of life. However, the theory of chemical evolution and heterotrophic origins of life requires major updating, which should include the abandonment of the idea that the appearance of life was a slow process involving billions of years. Stability of organic compounds and the genetics of bacteria suggest that the origin and early diversification of life took place in a time period of the order of 10 million years. Current evidence suggest that the abiotic synthesis of organic compounds may be a widespread phenomenon in the Galaxy and may have a deterministic nature. However, the history of the biosphere does not exhibits any obvious trend towards greater complexity or «higher» forms of life. Therefore, the role of contingency in biological evolution should not be understimated in the discussions of the possibilities of life in the Universe.

Photochemical Evolution of Interstellar/Precometary Organic Material

1997 ◽  
Vol 161 ◽  
pp. 23-47 ◽  
Author(s):  
Louis J. Allamandola ◽  
Max P. Bernstein ◽  
Scott A. Sandford
Keyword(s):  
Origin Of Life ◽  
Building Blocks ◽  
Complex Species ◽  
Infrared Observations ◽  
Interstellar Ice ◽  
Polycyclic Aromatic ◽  
Ultraviolet Photolysis ◽  
The Origin Of Life ◽  
Simple Molecules ◽  
Complex Organic

AbstractInfrared observations, combined with realistic laboratory simulations, have revolutionized our understanding of interstellar ice and dust, the building blocks of comets. Since comets are thought to be a major source of the volatiles on the primative earth, their organic inventory is of central importance to questions concerning the origin of life. Ices in molecular clouds contain the very simple molecules H2O, CH3OH, CO, CO2, CH4, H2, and probably some NH3and H2CO, as well as more complex species including nitriles, ketones, and esters. The evidence for these, as well as carbonrich materials such as polycyclic aromatic hydrocarbons (PAHs), microdiamonds, and amorphous carbon is briefly reviewed. This is followed by a detailed summary of interstellar/precometary ice photochemical evolution based on laboratory studies of realistic polar ice analogs. Ultraviolet photolysis of these ices produces H2, H2CO, CO2, CO, CH4, HCO, and the moderately complex organic molecules: CH3CH2OH (ethanol), HC(= O)NH2(formamide), CH3C(= O)NH2(acetamide), R-CN (nitriles), and hexamethylenetetramine (HMT, C6H12N4), as well as more complex species including polyoxymethylene and related species (POMs), amides, and ketones. The ready formation of these organic species from simple starting mixtures, the ice chemistry that ensues when these ices are mildly warmed, plus the observation that the more complex refractory photoproducts show lipid-like behavior and readily self organize into droplets upon exposure to liquid water suggest that comets may have played an important role in the origin of life.

Suicidal Behavior in Black South Africans

Crisis ◽  
2003 ◽  
Vol 24 (1) ◽  
pp. 24-28 ◽  
Author(s):  
Lourens Schlebusch ◽  
Naseema B.M. Vawda ◽  
Brenda A. Bosch
Keyword(s):  
South African ◽  
Suicidal Behavior ◽  
Health Care Facilities ◽  
South African Society ◽  
South Africans ◽  
The Past ◽  
The People ◽  
Care Facilities ◽  
Black South Africans ◽  
To Come

Summary: In the past suicidal behavior among Black South Africans has been largely underresearched. Earlier studies among the other main ethnic groups in the country showed suicidal behavior in those groups to be a serious problem. This article briefly reviews some of the more recent research on suicidal behavior in Black South Africans. The results indicate an apparent increase in suicidal behavior in this group. Several explanations are offered for the change in suicidal behavior in the reported clinical populations. This includes past difficulties for all South Africans to access health care facilities in the Apartheid (legal racial separation) era, and present difficulties of post-Apartheid transformation the South African society is undergoing, as the people struggle to come to terms with the deleterious effects of the former South African racial policies, related socio-cultural, socio-economic, and other pressures.

Screen Wonders of the Past: And to Come?

1957 ◽  
Vol 11 (4) ◽  
pp. 381-393
Author(s):  
Kenneth MacGowan
Keyword(s):  
The Past ◽  
To Come

Music and Memory: The Tlatelolco Refrain

2015 ◽  
Vol 2 (1) ◽  
Author(s):  
Josh Kun
Keyword(s):  
State Violence ◽  
First Century ◽  
Student Movements ◽  
Octavio Paz ◽  
Mexican History ◽  
The Past ◽  
Rock Bands ◽  
To Come ◽  
Musical Memory ◽  
A Current

Ever since the 1968 student movements and the events surrounding the Tlatelolco massacre, Mexico City rock bands have openly engaged with the intersection of music and memory. Their songs offer audiences a medium through which to come to terms with the events of the past as a means of praising a broken world, to borrow the poet Adam Zagajewski’s phrase. Contemporary songs such as Saúl Hernández’s “Fuerte” are a twenty-first-century voicing of the ceaseless revolutionary spirit that John Gibler has called “Mexico unconquered,” a current of rebellion and social hunger for justice that runs in the veins of Mexican history. They are the latest additions to what we might think about as “the Mexico unconquered songbook”: musical critiques of impunity and state violence that are rooted in the weaponry of memory, refusing to focus solely on the present and instead making connections with the political past. What Octavio Paz described as a “swash of blood” that swept across “the international subculture of the young” during the events in Tlatelolco Plaza on October 2, 1968, now becomes a refrain of musical memory and political consciousness that extends across eras and generations. That famous phrase of Paz’s is a reminder that these most recent Mexican musical interventions, these most recent formations of a Mexican subculture of the young, maintain a historically tested relationship to blood, death, loss, and violence.

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