Origin & Evolution of Life

Looking at The Limits for Life

By Keith Cowing
Status Report
Journal of the Royal Society Interface
September 10, 2015
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Looking at The Limits for Life
Early Earth – Smithsonian

Biological processes on the Earth operate within a parameter space that is constrained by physical and chemical extremes.

Aerobic respiration can result in adenosine triphosphate yields up to over an order of magnitude higher than those attained anaerobically and, under certain conditions, may enable microbial multiplication over a broader range of extremes than other modes of catabolism. We employed growth data published for 241 prokaryotic strains to compare temperature, pH and salinity values for cell division between aerobically and anaerobically metabolizing taxa. Isolates employing oxygen as the terminal electron acceptor exhibited a considerably more extensive three-dimensional phase space for cell division (90% of the total volume) than taxa using other inorganic substrates or organic compounds as the electron acceptor (15% and 28% of the total volume, respectively), with all groups differing in their growth characteristics.

Understanding the mechanistic basis of these differences will require integration of research into microbial ecology, physiology and energetics, with a focus on global-scale processes. Critical knowledge gaps include the combined impacts of diverse stress parameters on Gibbs energy yields and rates of microbial activity, interactions between cellular energetics and adaptations to extremes, and relating laboratory-based data to in situ limits for cell division.

Paper: Aerobically respiring prokaryotic strains exhibit a broader temperaturepHsalinity space for cell division than anaerobically respiring and fermentative strains

Jesse P. Harrison, Luke Dobinson, Kenneth Freeman, Ross McKenzie, Dale Wyllie, Sophie L. Nixon, Charles S. Cockell Published 9 September 2015.DOI: 10.1098/rsif.2015.0658

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