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Activity and stability of a complex bacterial soil community under simulated Martian conditions

Published online by Cambridge University Press:  04 October 2005

Aviaja Anna Hansen
Affiliation:
Department of Biological Sciences – Microbiology, University of Aarhus, DK-8000 Aarhus C, Denmark e-mail: Bente.Lomstein@biology.au.dk
Jonathan Merrison
Affiliation:
Department of Physics and Astronomy, University of Aarhus, DK-8000 Aarhus C, Denmark
Per Nørnberg
Affiliation:
Department of Earth Sciences, University of Aarhus, DK-8000 Aarhus C, Denmark
Bente Aagaard Lomstein
Affiliation:
Department of Biological Sciences – Microbiology, University of Aarhus, DK-8000 Aarhus C, Denmark e-mail: Bente.Lomstein@biology.au.dk
Kai Finster
Affiliation:
Department of Biological Sciences – Microbiology, University of Aarhus, DK-8000 Aarhus C, Denmark e-mail: Bente.Lomstein@biology.au.dk

Abstract

A simulation experiment with a complex bacterial soil community in a Mars simulation chamber was performed to determine the effect of Martian conditions on community activity, stability and survival. At three different depths in the soil core short-term effects of Martian conditions with and without ultraviolet (UV) exposure corresponding to 8 Martian Sol were compared. Community metabolic activities and functional diversity, measured as glucose respiration and versatility in substrate utilization, respectively, decreased after UV exposure, whereas they remained unaffected by Martian conditions without UV exposure. In contrast, the numbers of culturable bacteria and the genetic diversity were unaffected by the simulated Martian conditions both with and without UV exposure. The genetic diversity of the soil community and of the colonies grown on agar plates were evaluated by denaturant gradient gel electrophoresis (DGGE) on DNA extracts. Desiccation of the soil prior to experimentation affected the functional diversity by decreasing the versatility in substrate utilization. The natural dominance of endospores and Gram-positive bacteria in the investigated Mars-analogue soil may explain the limited effect of the Mars incubations on the survival and community structure. Our results suggest that UV radiation and desiccation are major selecting factors on bacterial functional diversity in terrestrial bacterial communities incubated under simulated Martian conditions. Furthermore, these results suggest that forward contamination of Mars is a matter of great concern in future space missions.

Type
Research Article
Copyright
2005 Cambridge University Press

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