Special Issue "The Physico-Chemical Limits of Life"


A special issue of Life (ISSN 2075-1729). This special issue belongs to the section "Hypotheses in the Life Sciences".

Deadline for manuscript submissions: closed (31 December 2014)

Special Issue Editors

Guest Editor
Prof. Dr. John A. Baross
School of Oceanography, University of Washington, Box 357940, Seattle, WA 98195 USA
Website: http://www.ocean.washington.edu
E-Mail: jbaross@u.washington.edu
Interests: life in estreme environments; limits of life; the origin and evolution of life on Earth; astrobiology and the search for life elsewhere

Guest Editor
Dr. William Bains
1. Department of Chemical Engineering and Biotechnology, University of Cambridge, Tennis Court Road, Cambridge CB2 1QT, UK
2 Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
Website: http://www.williambains.co.uk
E-Mail: bains@mit.edu
Interests: astrobiology; detection of life; limits of life; origin of life; nature of aging; anti-aging medicine; computational chemistry; science commercialization; biotechnology financing; venture capital

Special Issue Information

Dear Colleagues,

The vast majority of life on Earth lives at between 0.75 and 5 bar pressure and –5 oC and 30 oC temperature. However, we know that life can flourish substantially outside these limits. Recent decades have shown that life in the deep ocean, in hydrothermal systems or in crustal rocks may play a substantial role in the chemistry of Earth’s biosphere, and the discovery of a bewildering variety of planets around other stars suggest environments very different from Earth’s where we might nevertheless look for life. They have also shown that the abundant chemical and energy resources of the surface are not essential for life, and that cells with doubling times may in future decades grow in regions previously considered incapable of supporting metabolism. Our knowledge on the limits of life on Earth continues to expand as we explore more remote and seemingly inhospitable environments using advanced technologies. Laboratory experiments and theoretical studies hint that life could be based on molecular structures substantially different from those we know. So what are the physico–chemical limits of the environments in which any life, not just common terrestrial life, can flourish? This Special Issue explores these questions with the aim of increasing our knowledge about the fundamental nature of living beings (known or yet to be discovered by science), and also launches a new Section of Life—Life: Hypotheses in the Life Sciences. Life: HyLS will focus on new ideas, hypotheses and theoretical approaches to problems in the life sciences, starting with the question: What are the physico–chemical limits of life? The answers will inform where we search for life on Earth and elsewhere, but also synthetic attempts to build new life with useful capabilities.

Prof. Dr. John A. Baross
Dr. William Bains
Guest Editors


Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. Papers will be published continuously (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are refereed through a peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Life is an international peer-reviewed Open Access quarterly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 300 CHF (Swiss Francs). English correction and/or formatting fees of 250 CHF (Swiss Francs) will be charged in certain cases for those articles accepted for publication that require extensive additional formatting and/or English corrections.


  • alternative biochemistry
  • artificial life
  • bioenergetics
  • biological energy quantum
  • extremophiles
  • stability
  • synthetic biology
  • thermodynamics
  • macromolecular structure
  • LUCA

Published Papers (1 paper)

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Life 2015, 5(1), 1-3; doi:10.3390/life5010001
Received: 23 December 2014 / Accepted: 24 December 2014 / Published: 29 December 2014
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Planned Papers

The below list represents only planned manuscripts. Some of these manuscripts have not been received by the Editorial Office yet. Papers submitted to MDPI journals are subject to peer-review.

Title: Prediction of the Maximum Temperature for Life, Based on the Stability of Metabolites to Hydrolysis
William Bains1,*, Yao Xiao 2 and Changyong Yu 2
1 Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, 77 Mass. Avenue, Cambridge, MA 02139, USA
Department of Chemical Engineering and Biotechnology, University of Cambridge, Tennis Court Road, Cambridge CB2 1QT, UK
The components of life must be sufficiently stable to last long enough to perform their function in the chemical environment of the actively metabolizing cell. One of the most ubiquitous chemical degradation pathways, for organic chemicals in water, is hydrolysis. The rate of hydrolysis increases with increasing temperature, and, at some temperatures, the rate of spontaneous hydrolysis of the components of life will be too fast for life to repair the resulting damage. In principle, therefore, we can predict a maximum temperature above which an active terrestrial metabolism cannot function—because spontaneous hydrolysis will break its components down faster than they can be synthesized or repaired—by analysis of the hydrolysis rates of the components of life and comparison of that rate with their minimum half-lives in metabolism. The present study is a first step in this direction, analyzing the hydrolytic stability of small molecule metabolites based on literature data. We searched the scientific literature for data on the kinetics of hydrolysis of metabolites or related small molecules. Assuming that the hydrolysis followed an Arrhenius first order rate equation, we extracted hydrolysis rate constants from 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 an arbitrary temperature.  The results of this preliminary study show there is minimal reliable data on metabolite hydrolysis rates in the literature, the data available is almost entirely confined to a small number of classes of chemicals, and the data available is often mutually contradictory because of varying reaction conditions. However, a preliminary analysis suggests that terrestrial biochemistry is limited to environments below ~130 ºC – 140 ºC. We comment briefly on why pressure is likely to have little effect on this, although, in this regard, data is even sparser. We finish with some speculations on what aspects of the “consensus” biochemistry of surface-dwelling life might be most susceptible to high temperature hydrolysis, and hence might be different in a deep rock “alternative biosphere”.

Last update: 29 July 2014

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