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A Survey of Environmental Microbial Flora During Closed Chamber StudiesServices, Inc. and NASA Johnson Space Center, Houston, TX As NASA prepares for long-term missions aboard the International Space Station and the eventual exploration of Mars, closed-environment chambers on Earth have become important test beds for systems evaluations. During 2 separate studies of a selfcontained ecosystem containing 4 crewmembers, microbial surveys of samples from 13 surface and 3 air sites were performed. Microbial concentration of samples from surface sites with frequent water contact (e.g., urinal, sink) did not indicate significantly higher levels of contamination than drier areas, though surface cleaning by the crew may have influenced this conclusion. Changes in bacterial diversity on surface sites implied that the number of transient species was high, suggesting movement by crew activities, aerosols, or both. A non-linear relationship between bacterial diversity and enumeration from surface samples indicated that a rapid increase occurred in the number of species as cell concentration increased to 5 CFU/sq cm. Above this concentration, the number of different bacterial species varied between 11 and 16. Airborne bacteria and fungi averaged only 160 and 1 CFU/m3, respectively. Microbial contamination of the potable water system primarily consisted of 3 species of Gram negative bacteria; however, after 60 days during one study, several species of Bacillus became the dominant flora. This study suggests that under these conditions, microbial contamination in the air and water was suppressed by the life-support systems, though contamination was possible. Conversely, the crew and their activities controlled microbial levels on surfaces. Understanding the factors that affect microbial control will improve the design of microbial testing both during space flight and in analogous Earth-based environments.
Document ID
20000085927
Acquisition Source
Johnson Space Center
Document Type
Preprint (Draft being sent to journal)
Authors
Ott, C. Mark
(Enterprise Advisory Services, Inc. Houston, TX United States)
Groves, Theron O.
(Enterprise Advisory Services, Inc. Houston, TX United States)
Bell-Robinson, Denetia
(Enterprise Advisory Services, Inc. Houston, TX United States)
Pierson, Duane L.
(NASA Johnson Space Center Houston, TX United States)
Paloski, W. H.
Date Acquired
August 19, 2013
Publication Date
January 1, 1999
Subject Category
Life Sciences (General)
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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