Exposure of DNA and Bacillus subtilis spores to simulated martian environments: use of quantitative PCR (qPCR) to measure inactivation rates of DNA to function as a template molecule.
Several NASA and ESA missions are planned for the next decade to investigate the possibility of present or past life on Mars. Evidence of extraterrestrial life will likely rely on the detection of biomolecules, which highlights the importance of preventing forward contamination not only with viable microorganisms but also with biomolecules that could compromise the validity of life-detection experiments. The designation of DNA as a high-priority biosignature makes it necessary to evaluate its persistence in extraterrestrial environments and the effects of those conditions on its biological activity. We exposed DNA deposited on spacecraft-qualified aluminum coupons to a simulated martian environment for periods ranging from 1 minute to 1 hour and measured its ability to function as a template for replication in a quantitative polymerase chain reaction (qPCR) assay. We found that inactivation of naked DNA or DNA extracted from exposed spores of Bacillus subtilis followed a multiphasic UV-dose response and that a fraction of DNA molecules retained functionality after 60 minutes of exposure to simulated full-spectrum solar radiation in martian atmospheric conditions. The results indicate that forward-contaminant DNA could persist for considerable periods of time at the martian surface.
Department of Microbiology and Cell Science, University of Florida , Kennedy Space Center, Florida 32899, USA. WLN@ufl.edu
Patricia
P
Fajardo-Cavazos
Andrew C
AC
Schuerger
Wayne L
WL
Nicholson
D000388:Air; D001412:Bacillus subtilis / Q000235:genetics* / Q000528:radiation effects; D002876:Chromosomes, Bacterial / Q000528:radiation effects; D004269:DNA, Bacterial / Q000235:genetics* / Q000528:radiation effects; D004781:Environmental Exposure / Q000032:analysis; D005118:Extraterrestrial Environment; D018535:Mars; D050296:Microbial Viability / Q000528:radiation effects; D010957:Plasmids / Q000235:genetics; D016133:Polymerase Chain Reaction; D012015:Reference Standards; D018561:Space Simulation; D013056:Spectrophotometry, Ultraviolet; D013171:Spores, Bacterial / Q000235:genetics* / Q000528:radiation effects; D013698:Templates, Genetic; D014466:Ultraviolet Rays
D004269:DNA, Bacterial