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Growth of the acidophilic iron–sulfur bacterium Acidithiobacillus ferrooxidans under Mars-like geochemical conditions

Bauermeister, Anja and Rettberg, Petra and Flemming, Hans-Curt (2013) Growth of the acidophilic iron–sulfur bacterium Acidithiobacillus ferrooxidans under Mars-like geochemical conditions. Planetary and Space Science, Epub ahead of print (in Press). Elsevier. DOI: 10.1016/j.pss.2013.09.009 ISSN 0032-0633

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Abstract

The question of life on Mars has been in focus of astrobiological research for several decades, and recent missions in orbit or on the surface of the planet are constantly expanding our knowledge on Martian geochemistry. For example, massive stratified deposits have been identified on Mars containing sulfate minerals and iron oxides, which suggest the existence of acidic aqueous conditions in the past, similar to acidic iron- and sulfur-rich environments on Earth. Acidophilic organisms thriving in such habitats could have been an integral part of a possibly widely extinct Martian ecosystem, but remains might possibly even exist today in protected subsurface niches. The chemolithoautotrophic strain Acidithiobacillus ferrooxidans was selected as a model organism to study the metabolic capacities of acidophilic iron–sulfur bacteria, especially regarding their ability to grow with in situ resources that could be expected on Mars. The experiments were not designed to accurately simulate Martian physical conditions (except when certain single parameters such as oxygen partial pressure were considered), but rather the geochemical environment that can be found on Mars. A. ferrooxidans could grow solely on the minerals contained in synthetic Mars regolith mixtures with no added nutrients, using either O₂as an external electron acceptor for iron oxidation, or H₂as an external electron donor for iron reduction, and thus might play important roles in the redox cycling of iron on Mars. Though the oxygen partial pressure of the Martian atmosphere at the surface was not sufficient for detectable iron oxidation and growth of A. ferrooxidans during short-term incubation (7 days), alternative chemical O₂-generating processes in the subsurface might yield microhabitats enriched in oxygen, which principally are possible under such conditions. The bacteria might also contribute to the reductive dissolution of Fe³⁺-containing minerals like goethite and hematite, which are characterized by a high thermodynamic stability. Even in a desiccated environment, A. ferrooxidans survived for one week under simulated Martian shallow subsurface conditions (6 hPa, −20 °C, 0.13% O₂) in the form of dried biofilms without loss of viability. Low temperature and low oxygen pressure were favorable to survival. Thus, the acidophilic iron–sulfur bacterium A. ferrooxidans may be considered a plausible candidate of a potential Martian food web based on its metabolic capacities. As an autotroph it would be located at the base of such a food web, providing organic carbon.

Item URL in elib:https://elib.dlr.de/84862/
Document Type:Article
Title:Growth of the acidophilic iron–sulfur bacterium Acidithiobacillus ferrooxidans under Mars-like geochemical conditions
Authors:
AuthorsInstitution or Email of AuthorsAuthors ORCID iD
Bauermeister, Anja German Aerospace Center DLR e.V., Institute of Aerospace Medicine, Radiation Biology, Linder Höhe, D-51147 Köln (Cologne), GermanyUNSPECIFIED
Rettberg, PetraGerman Aerospace Center DLR e.V., Institute of Aerospace Medicine, Radiation Biology, Linder Höhe, D-51147 Köln (Cologne), GermanyUNSPECIFIED
Flemming, Hans-CurtUniversity of Duisburg-Essen, Faculty of Chemistry, Biofilm Centre, Universitätsstr.5, D-45141 Essen, GermanyUNSPECIFIED
Date:2013
Journal or Publication Title:Planetary and Space Science
Refereed publication:Yes
Open Access:No
Gold Open Access:No
In SCOPUS:Yes
In ISI Web of Science:Yes
Volume:Epub ahead of print (in Press)
DOI :10.1016/j.pss.2013.09.009
Publisher:Elsevier
ISSN:0032-0633
Status:Published
Keywords:Acidophilic iron–sulfur bacteria, Mars, Minerals, Microbial food web
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Space
HGF - Program Themes:Research under Space Conditions
DLR - Research area:Raumfahrt
DLR - Program:R FR - Forschung unter Weltraumbedingungen
DLR - Research theme (Project):R - Vorhaben Strahlenbiologie
Location: Köln-Porz
Institutes and Institutions:Institute of Aerospace Medicine > Radiation Biology
Deposited By: Kopp, Kerstin
Deposited On:25 Oct 2013 11:46
Last Modified:25 Oct 2013 11:46

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