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Applied and Environmental Microbiology, August 2008, p. 5159-5167, Vol. 74, No. 16
0099-2240/08/$08.00+0     doi:10.1128/AEM.00891-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

Persistence of Biomarker ATP and ATP-Generating Capability in Bacterial Cells and Spores Contaminating Spacecraft Materials under Earth Conditions and in a Simulated Martian Environment{triangledown}

Patricia Fajardo-Cavazos,1 Andrew C. Schuerger,2 and Wayne L. Nicholson1*

Departments of Microbiology and Cell Science,1 Plant Pathology, University of Florida, Kennedy Space Center, Florida 328992

Received 18 April 2008/ Accepted 11 June 2008

Most planetary protection research has concentrated on characterizing viable bioloads on spacecraft surfaces, developing techniques for bioload reduction prior to launch, and studying the effects of simulated martian environments on microbial survival. Little research has examined the persistence of biogenic signature molecules on spacecraft materials under simulated martian surface conditions. This study examined how endogenous adenosine-5'-triphosphate (ATP) would persist on aluminum coupons under simulated martian conditions of 7.1 mbar, full-spectrum simulated martian radiation calibrated to 4 W m–2 of UV-C (200 to 280 nm), –10°C, and a Mars gas mix of CO2 (95.54%), N2 (2.7%), Ar (1.6%), O2 (0.13%), and H2O (0.03%). Cell or spore viabilities of Acinetobacter radioresistens, Bacillus pumilus, and B. subtilis were measured in minutes to hours, while high levels of endogenous ATP were recovered after exposures of up to 21 days. The dominant factor responsible for temporal reductions in viability and loss of ATP was the simulated Mars surface radiation; low pressure, low temperature, and the Mars gas composition exhibited only slight effects. The normal burst of endogenous ATP detected during spore germination in B. pumilus and B. subtilis was reduced by 1 or 2 orders of magnitude following, respectively, 8- or 30-min exposures to simulated martian conditions. The results support the conclusion that endogenous ATP will persist for time periods that are likely to extend beyond the nominal lengths of most surface missions on Mars, and planetary protection protocols prior to launch may require additional rigor to further reduce the presence and abundance of biosignature molecules on spacecraft surfaces.

* Corresponding author. Mailing address: Space Life Sciences Laboratory, Building M6-1025/SLSL, Room 201-B, Kennedy Space Center, FL 32899. Phone: (321) 861-3487. Fax: (321) 861-2925. E-mail: WLN{at}ufl.edu

{triangledown} Published ahead of print on 20 June 2008.

Applied and Environmental Microbiology, August 2008, p. 5159-5167, Vol. 74, No. 16
0099-2240/08/$08.00+0     doi:10.1128/AEM.00891-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.





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