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Aerts JW, Sarbu SM, Brad T, Ehrenfreund P, Westerhoff HV. Microbial Ecosystems in Movile Cave: An Environment of Extreme Life. Life (Basel) 2023; 13:2120. [PMID: 38004260 PMCID: PMC10672346 DOI: 10.3390/life13112120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2023] [Revised: 10/21/2023] [Accepted: 10/24/2023] [Indexed: 11/26/2023] Open
Abstract
Movile Cave, situated in Romania close to the Black Sea, constitutes a distinct and challenging environment for life. Its partially submerged ecosystem depends on chemolithotrophic processes for its energetics, which are fed by a continuous hypogenic inflow of mesothermal waters rich in reduced chemicals such as hydrogen sulfide and methane. We sampled a variety of cave sublocations over the course of three years. Furthermore, in a microcosm experiment, minerals were incubated in the cave waters for one year. Both endemic cave samples and extracts from the minerals were subjected to 16S rRNA amplicon sequencing. The sequence data show specific community profiles in the different subenvironments, indicating that specialized prokaryotic communities inhabit the different zones in the cave. Already after one year, the different incubated minerals had been colonized by specific microbial communities, indicating that microbes in Movile Cave can adapt in a relatively short timescale to environmental opportunities in terms of energy and nutrients. Life can thrive, diversify and adapt in remote and isolated subterranean environments such as Movile Cave.
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Affiliation(s)
- Joost W. Aerts
- Molecular Cell Biology, A-LIFE, 01-E-57, Faculty of Science, VU University Amsterdam, Van der Boechorstraat 3, 1081 BT Amsterdam, The Netherlands
| | - Serban M. Sarbu
- “Emil Racoviţă” Institute of Speleology, Str. Frumoasă 31, 010986 Bucharest, Romania
- Department of Biological Sciences, California State University, Chico, CA 95929, USA
| | - Traian Brad
- “Emil Racoviţă” Institute of Speleology, Clinicilor 5-7, 400006 Cluj-Napoca, Romania;
| | - Pascale Ehrenfreund
- Laboratory for Astrophysics, Leiden Observatory, Leiden University, 2333 RA Leiden, The Netherlands
- Space Policy Institute, George Washington University, Washington, DC 20052, USA
| | - Hans V. Westerhoff
- Molecular Cell Biology, A-LIFE, 01-E-57, Faculty of Science, VU University Amsterdam, Van der Boechorstraat 3, 1081 BT Amsterdam, The Netherlands
- Synthetic Systems Biology and Nuclear Organization, Swammerdam Institute for Life Sciences, University of Amsterdam, 1098 XH Amsterdam, The Netherlands
- School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester M13 9PL, UK
- Stellenbosch Institute for Advanced Study, Stellenbosch 7600, South Africa
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Shkrob IA, Chemerisov SD, Marin TW. Photocatalytic decomposition of carboxylated molecules on light-exposed martian regolith and its relation to methane production on Mars. ASTROBIOLOGY 2010; 10:425-436. [PMID: 20528197 DOI: 10.1089/ast.2009.0433] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
We propose that the paucity of organic compounds in martian soil can be accounted for by efficient photocatalytic decomposition of carboxylated molecules due to the occurrence of the photo-Kolbe reaction at the surface of particulate iron(III) oxides that are abundant in the martian regolith. This photoreaction is initiated by the absorption of UVA light, and it readily occurs even at low temperature. The decarboxylation is observed for miscellaneous organic carboxylates, including the nonvolatile products of kerogen oxidation (that are currently thought to accumulate in the soil) as well as alpha-amino acids and peptides. Our study indicates that there may be no "safe haven" for these organic compounds on Mars; oxidation by reactive radicals, such as hydroxyl, is concerted with photocatalytic reactions on the oxide particles. Acting together, these two mechanisms result in mineralization of the organic component. The photooxidation of acetate (the terminal product of radical oxidation of the aliphatic component of kerogen) on the iron(III) oxides results in the formation of methane; this reaction may account for seasonably variable production of methane on Mars. The concomitant reduction of Fe(III) in the regolith leads to the formation of highly soluble ferrous ions that contribute to weathering of the soil particles.
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Affiliation(s)
- Ilya A Shkrob
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Argonne, Illinois 60439, USA.
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Krinsley D, Dorn RI, DiGregorio B. Astrobiological implications of rock varnish in Tibet. ASTROBIOLOGY 2009; 9:551-562. [PMID: 19663762 DOI: 10.1089/ast.2008.0238] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
The study of terrestrial geomicrobiology and its relationship to rock weathering processes is an essential tool in developing analogues for similar processes that may have occurred on Mars. Most studies of manganese-enhanced rock varnish have focused on samples taken from warm arid desert regions. Here, we examine samples obtained from eolian-abraded lava flows of the 4700-4800 m high Ashikule Basin in Tibet. Because it receives approximately 300 mm of precipitation annually, this site is nowhere near as dry as Atacama Desert locales. However, the dusty, sulfate-rich, high-altitude and high-UV flux environment of the Tibetan locale offers new insight into rock varnish formation processes in a terrestrial environment that displays some attributes similar to those expected on early Mars. Microprobe measurements reveal that Mn enhancements in varnish are two orders of magnitude above the dust source, but Fe is only enhanced by a factor of three. Manganese-enhancing bacterial forms are not abundant but are still approximately 3 times more common than in Mojave and Sonoran Desert varnishes. In addition to its occurrence in subaerial positions, Tibetan varnish also occurs in micron-scale "pods" enveloped by silica glaze and as remobilized constituents that have migrated into the underlying weathering rind. A lack of surficial Mn-rich varnish, therefore, might not imply the absence of varnish. In contrast to suggestions that silica glaze might be a good source of microbial fossils and a key to varnish formation, we did not observe any clear microfossil forms entombed in silica glaze; further, there is no gradation between varnish and silica glaze but only distinct contacts.
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Affiliation(s)
- David Krinsley
- Department of Geological Sciences, University of Oregon, Eugene, Oregon 97403-1272, USA.
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Zahnle K, Haberle RM, Catling DC, Kasting JF. Photochemical instability of the ancient Martian atmosphere. ACTA ACUST UNITED AC 2008. [DOI: 10.1029/2008je003160] [Citation(s) in RCA: 104] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
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Tosca NJ, McLennan SM, Dyar MD, Sklute EC, Michel FM. Fe oxidation processes at Meridiani Planum and implications for secondary Fe mineralogy on Mars. ACTA ACUST UNITED AC 2008. [DOI: 10.1029/2007je003019] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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