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Multiplication of microbes below 0.690 water activity: Implications for terrestrial and extraterrestrial life

Stevenson, A and Burkhardt, J and Cockell, CS and Cray, JA and Dijksterhuis, J and Fox-Powell, M and Kee, TP and Kminek, G and Mcgenity, TJ and Timmis, KN and Timson, DJ and Voytek, MA and Westall, F and Yakimov, MM and Hallsworth, JE (2015) 'Multiplication of microbes below 0.690 water activity: Implications for terrestrial and extraterrestrial life.' Environmental Microbiology, 17 (2). 257 - 277. ISSN 1462-2912

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Abstract

© 2015 Society for Applied Microbiology and John Wiley & Sons Ltd. Since a key requirement of known life forms is available water (water activity; aw), recent searches for signatures of past life in terrestrial and extraterrestrial environments have targeted places known to have contained significant quantities of biologically available water. However, early life on Earth inhabited high-salt environments, suggesting an ability to withstand low water-activity. The lower limit of water activity that enables cell division appears to be ~0.605 which, until now, was only known to be exhibited by a single eukaryote, the sugar-tolerant, fungal xerophile Xeromyces bisporus. The first forms of life on Earth were, though, prokaryotic. Recent evidence now indicates that some halophilic Archaea and Bacteria have water-activity limits more or less equal to those of X.bisporus. We discuss water activity in relation to the limits of Earth's present-day biosphere; the possibility of microbial multiplication by utilizing water from thin, aqueous films or non-liquid sources; whether prokaryotes were the first organisms able to multiply close to the 0.605-aw limit; and whether extraterrestrial aqueous milieux of ≥0.605aw can resemble fertile microbial habitats found on Earth.

Item Type: Article
Subjects: Q Science > QH Natural history > QH301 Biology
Divisions: Faculty of Science and Health > Biological Sciences, School of
Depositing User: Jim Jamieson
Date Deposited: 15 Oct 2014 10:58
Last Modified: 23 Jan 2019 02:15
URI: http://repository.essex.ac.uk/id/eprint/10856

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