Prediction of the maximum temperature for life based on the stability of metabolites to decomposition in water.

William Bains,Yao Xiao,Changyong Yu

doi:10.3390/life5021054

William Bains, Yao Xiao + Show 1 more

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https://doi.org/10.3390/life5021054

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Abstract

The components of life must survive in a cell long enough to perform their function in that cell. Because the rate of attack by water increases with temperature, we can, in principle, predict a maximum temperature above which an active terrestrial metabolism cannot function by analysis of the decomposition rates of the components of life, and comparison of those rates with the metabolites’ minimum metabolic half-lives. The present study is a first step in this direction, providing an analytical framework and method, and analyzing the stability of 63 small molecule metabolites based on literature data. Assuming that attack by water follows a first order rate equation, we extracted decomposition rate constants from literature data and estimated their statistical reliability. The resulting rate equations were then used to give a measure of confidence in the half-life of the metabolite concerned at different temperatures. There is little reliable data on metabolite decomposition or hydrolysis rates in the literature, the data is mostly confined to a small number of classes of chemicals, and the data available are sometimes mutually contradictory because of varying reaction conditions. However, a preliminary analysis suggests that terrestrial biochemistry is limited to environments below ~150–180 °C. We comment briefly on why pressure is likely to have a small effect on this.

Highlights

Temperature is a physical state variable that has profound effects on all of chemistry, and on all of biology [1]
We explored the use of weighted least squares fit to the kinetic data, which takes the errors in estimating k into account: in general, this did not lead to systematically improved confidence [39,40], and so simple linear best fit was adopted as standard for this study
Two papers were found with appropriate kinetics data for the decomposition of Fructose [46,47]

Summary

Introduction

Temperature is a physical state variable that has profound effects on all of chemistry, and on all of biology [1]. The limiting temperature above which life cannot flourish is of theoretical and practical importance to many biological and geochemical studies [2]. Terrestrial organisms are found to grow in a relatively narrow range of temperatures, between −20 °C and ~120 °C [1]. The lowest temperature compatible with life is set by the physical properties of water [3]. Organisms growing at extreme temperatures have similar biochemistry to mesophilic organisms such as ourselves, based on proteins, nucleic acids, carbohydrates, etc., and with much of their metabolic machinery functionally identical (reviewed in [10]). Adaptation to high temperatures involves many, relatively minor changes in biochemistry

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