Microbial Diversity and Biosignatures: An Icy Moons Perspective

Type Article
Date 2020-01
Language English
Author(s) Jebbar Mohamed1, Hickman-Lewis Keyron2, Cavalazzi Barbara3, Taubner Ruth-Sophie4, Rittmann Simon K.-M. R.5, Antunes Andre6
Affiliation(s) 1 : Univ. Brest, CNRS, Ifremer, Laboratoire de Microbiologie des Environnements Extrêmes, 29280, Plouzané, France
2 : Dipartimento di Scienze Biologiche, Geologiche e Ambientali, Università di Bologna, Bologna, Italy
3 : Centre de Biophysique Moléculaire, CNRS, Rue Charles Sadron, 45071, Orléans, France
4 : Department of Geology, University of Johannesburg, APK Campus, Johannesburg, South Africa
5 : Archaea Physiology & Biotechnology Group, Archaea Biology and Ecogenomics Division, Department of Ecogenomics and Systems Biology, Universität Wien, Wien, Austria
6 : State Key Laboratory of Lunar and Planetary Sciences, Macau University of Science and Technology (MUST), Taipa, Macau SAR, China
Source Space Science Reviews (0038-6308) (Springer Science and Business Media LLC), 2020-01 , Vol. 216 , N. 1 , P. 10 (47p.)
DOI 10.1007/s11214-019-0620-z
WOS© Times Cited 2
Keyword(s) Extremophiles, Prokaryotes, Metabolism, Diversity, Adaptation, Space explorat
Abstract

The icy moons of the outer Solar System harbor potentially habitable environments for life, however, compared to the terrestrial biosphere, these environments are characterized by extremes in temperature, pressure, pH, and other physico-chemical conditions. Therefore, the search for life on these icy worlds is anchored on the study of terrestrial extreme environments (termed “analogue sites”), which harbor microorganisms at the frontiers of polyextremophily. These so-called extremophiles have been found in areas previously considered sterile: hot springs, hydrothermal vents, acidic or alkaline lakes, hypersaline environments, deep sea sediments, glaciers, and arid areas, amongst others. Such model systems and communities in extreme terrestrial environments may provide important information relevant to the astrobiology of icy bodies, including the composition of potential biological communities and the identification of biosignatures that they may produce.

Extremophiles can use either sunlight (phototrophs) or chemical energy (chemotrophs) as energy sources, and different chemical compounds as electron donors or acceptors. Aerobic microorganisms use oxygen (O2) as a terminal electron acceptor, whereas anaerobic microorganisms may use nitrate (NO−3

), sulfate (SO2−4

), carbon dioxide (CO2), Fe(III), or other organic or inorganic molecules during respiration. The phylogenetic diversity of extremophiles is very high, leading to their broad dispersal across the phylogenetic tree of life together with a wide variety in metabolic diversity.

Some metabolisms are specific to archaea, for example, methanogenesis, an anaerobic respiration during which methane (CH4) is produced. Also sulfur-reduction performed by some bacteria and archaea is considered as a primitive metabolism which is restricted to anoxic sulfur-rich habitats in nature.

Methanogenesis and sulfur reduction are of specific interest for icy moon research as it might be one of the few known terrestrial metabolisms possible on these celestial bodies.

Therefore, the adaptation of these intriguing microorganisms to extreme conditions will be highlighted within this review.

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