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Effects of a simulated martian UV flux on the cyanobacterium, Chroococcidiopsis sp. 029

Cockell, C.; Schuerger, A. C.; Billi, D.; Friedmann, E. I. and Panitz, C. (2005). Effects of a simulated martian UV flux on the cyanobacterium, Chroococcidiopsis sp. 029. Astrobiology, 5(2) pp. 127–140.

DOI (Digital Object Identifier) Link: http://dx.doi.org/10.1089/ast.2005.5.127
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Abstract

Dried monolayers of Chroococcidiopsis sp. 029, a desiccation-tolerant, endolithic cyanobacterium, were exposed to a simulated martian-surface UV and visible light flux, which may also approximate to the worst-case scenario for the Archean Earth. After 5 min, there was a 99% loss of cell viability, and there were no survivors after 30 min. However, this survival was approximately 10 times higher than that previously reported for Bacillus subtilis. We show that under 1 mm of rock, Chroococcidiopsis sp. could survive (and potentially grow) under the high martian UV flux if water and nutrient requirements for growth were met. In isolated cells, phycobilisomes and esterases remained intact hours after viability was lost. Esterase activity was reduced by 99% after a 1-h exposure, while 99% loss of autofluorescence required a 4-h exposure. However, cell morphology was not changed, and DNA was still detectable by 4',6-diamidino-2-phenylindole staining after an 8-h exposure (equivalent to approximately 1 day on Mars at the equator). Under 1 mm of simulant martian soil or gneiss, the effect of UV radiation could not be detected on esterase activity or autofluorescence after 4 h. These results show that under the intense martian UV flux the morphological signatures of life can persist even after viability, enzymatic activity, and pigmentation have been destroyed. Finally, the global dispersal of viable, isolated cells of even this desiccation-tolerant, ionizing-radiation-resistant microorganism on Mars is unlikely as they are killed quickly by unattenuated UV radiation when in a desiccated state. These findings have implications for the survival of diverse microbial contaminants dispersed during the course of human exploratory class missions on the surface of Mars.

Item Type: Journal Article
Copyright Holders: 2005 Mary Ann Liebert, Inc.
ISSN: 1557-8070
Academic Unit/Department: Science > Physical Sciences
Interdisciplinary Research Centre: Centre for Earth, Planetary, Space and Astronomical Research (CEPSAR)
Item ID: 7991
Depositing User: Kyra Proctor
Date Deposited: 12 Jun 2007
Last Modified: 02 Jul 2014 15:03
URI: http://oro.open.ac.uk/id/eprint/7991
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