Stratospheric microbiology at 20 km over the Pacific Ocean
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An aerobiology sampling flight at 20 km was conducted on 28 April 2008 over the Pacific Ocean (36.5° N, 118–149° W), a period of time that coincided with the movement of Asian dust across the ocean. The aim of this study was to confirm the presence of viable bacteria and fungi within a transoceanic, atmospheric bridge and to improve the resolution of flight hardware processing techniques. Isolates of the microbial strains recovered were analyzed with ribosomal ribonucleic acid (rRNA) sequencing to identify bacterial species Bacillus sp., Bacillus subtilis, Bacillus endophyticus, and the fungal genus Penicillium. Satellite imagery and ground-based radiosonde observations were used to measure dust movement and characterize the high-altitude environment at the time of collection. Considering the atmospheric residency time (7–10 days), the extreme temperature regime of the environment (−75°C), and the absence of a mechanism that could sustain particulates at high altitude, it is unlikely that our samples indicate a permanent, stratospheric ecosystem. However, the presence of viable fungi and bacteria in transoceanic stratosphere remains relevant to understanding the distribution and extent of microbial life on Earth.
KeywordsUpper atmosphere Stratosphere Microbiology Pacific Ocean
This work was supported by the National Science Foundation Integrative Graduate Education and Research Traineeship (IGERT) program at the University of Washington Graduate Program in Astrobiology, and the NASA Academy at Ames Research Center. Critical resources came from NASA Johnson Space Center, NASA Kennedy Space Center, NASA Dryden Flight Research Center, United States Geological Survey (USGS), Lockheed Martin Corporation and the University of Florida. The authors are grateful to Jack Warren, Ron Bastien, and Mike Zolensky of the NASA Cosmic Dust Program for providing the flight hardware and Dennis Gearhart and Mike Kapitzke for coordinating the flight operations at Dryden. Special thanks is owed to the NASA Academy Staff (Doug O’Handley, Kathleen Hinds, Steve Mitchell, and Yvonne Torres) and 2007 Research Associates (Brandon Suarez, Erin Mulholland, Graham Lau, Jennifer Kissinger, Robert Haynes, Julia Ling, Jason Carroll, Jon Mihaly, Cameron Haag, Rick Conrey, Michael Kru, and Marc Silicani) who played a crucial role in coordinating this study. Atmospheric weather models were generated with the help of Doug Westphal (Naval Research Laboratory), Dave Dempsey (San Francisco State University), and Marion Legg (NASA Ames).
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