International Journal of Astrobiology

Table of Contents - 2005 - Volume 4, Issue 02  


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

Aviaja Anna Hansen a1, Jonathan Merrison a2, Per Nørnberg a3, Bente Aagaard Lomstein a1 and Kai Finster a1
a1 Department of Biological Sciences – Microbiology, University of Aarhus, DK-8000 Aarhus C, Denmark e-mail: Bente.Lomstein@biology.au.dk
a2 Department of Physics and Astronomy, University of Aarhus, DK-8000 Aarhus C, Denmark
a3 Department of Earth Sciences, University of Aarhus, DK-8000 Aarhus C, Denmark

Article author query
hansen aa   [PubMed][Google Scholar] 
merrison j   [PubMed][Google Scholar] 
nornberg p   [PubMed][Google Scholar] 
lomstein ba   [PubMed][Google Scholar] 
finster k   [PubMed][Google Scholar] 

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.

(Received February 8 2005)
(Accepted June 27 2005)


Key Words: bacterial community; desiccation; exobiology; Mars; soil; ultraviolet radiation.