Primordial soup was edible: abiotically produced Miller-Urey mixture supports bacterial growth.

Xueshu Xie,Leopold L Ilag,Daniel Backman,Albert T Lebedev,Liying Jiang,Viatcheslav B Artaev,Roman A Zubarev

doi:10.1038/srep14338

Xueshu Xie, Leopold L Ilag + Show 5 more

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https://doi.org/10.1038/srep14338

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Abstract

Sixty years after the seminal Miller-Urey experiment that abiotically produced a mixture of racemized amino acids, we provide a definite proof that this primordial soup, when properly cooked, was edible for primitive organisms. Direct admixture of even small amounts of Miller-Urey mixture strongly inhibits E. coli bacteria growth due to the toxicity of abundant components, such as cyanides. However, these toxic compounds are both volatile and extremely reactive, while bacteria are highly capable of adaptation. Consequently, after bacterial adaptation to a mixture of the two most abundant abiotic amino acids, glycine and racemized alanine, dried and reconstituted MU soup was found to support bacterial growth and even accelerate it compared to a simple mixture of the two amino acids. Therefore, primordial Miller-Urey soup was perfectly suitable as a growth media for early life forms.

Highlights

Sixty years after the seminal Miller-Urey experiment that abiotically produced a mixture of racemized amino acids, we provide a definite proof that this primordial soup, when properly cooked, was edible for primitive organisms
The simplest biologically useful amino acids are present — mostly glycine and alanine, that together compose 1–3% of the solid residue, as well as smaller amounts of other biological amino acids[10]. Both L- and D- chiral forms of amino acids are produced in roughly equal amounts, even though a recent report suggests that biologically relevant L-forms may be somewhat more abundant[11]
A small (≈ 3%) admixture of the MU mixture obtained after 5–8 days of MU experiment inhibited E. coli growth in sample wells, and in control wells

Summary

Introduction

Sixty years after the seminal Miller-Urey experiment that abiotically produced a mixture of racemized amino acids, we provide a definite proof that this primordial soup, when properly cooked, was edible for primitive organisms. Direct admixture of even small amounts of Miller-Urey mixture strongly inhibits E. coli bacteria growth due to the toxicity of abundant components, such as cyanides These toxic compounds are both volatile and extremely reactive, while bacteria are highly capable of adaptation. The organic molecules necessary for life have been created in the atmosphere of early Earth by such forces as lightning, electric discharges from the sun wind, ultraviolet light and meteorites. It has been argued that, besides highly toxic for some organisms gaseous CO, as well as aldehydes and cyanides in solution, the Miller-Urey mixture (MU mixture) contains D-amino acids that, according to some research[15,16], can be toxic to biological organisms[14]

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