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Microbial Characterization during the Early Habitation of the International Space Station


An evaluation of the microbiota from air, water, and surface samples provided a baseline of microbial characterization onboard the International Space Station (ISS) to gain insight into bacterial and fungal contamination during the initial stages of construction and habitation. Using 16S genetic sequencing and rep-PCR, 63 bacterial strains were isolated for identification and fingerprinted for microbial tracking. Of the bacterial strains that were isolated and fingerprinted, 19 displayed similarity to each other. The use of these molecular tools allowed for the identification of bacteria not previously identified using automated biochemical analysis and provided a clear indication of the source of several ISS contaminants. Strains of Bradyrhizobium and Sphingomonas unable to be identified using sequencing were identified by comparison of rep-PCR DNA fingerprints. Distinct DNA fingerprints for several strains of Methylobacterium provided a clear indication of the source of an ISS water supply contaminant. Fungal and bacterial data acquired during monitoring do not suggest there is a current microbial hazard to the spacecraft, nor does any trend indicate a potential health risk. Previous spacecraft environmental analysis indicated that microbial contamination will increase with time and will require continued surveillance.

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The authors thank Bacterial BarCodes, Inc., for their contribution in the processing and analysis of rep-PCR bacterial fingerprinting. We thank Jane Krauhs of Wyle Laboratories, Inc., for technical editing, and James R. Lupski, M.D., Ph.D., for his review of this manuscript. We also thank the crew of the ISS for sample collection and processing, the ISS Program Office, and the Microbiology Laboratory at the Johnson Space Center. This study was supported by NASA contract NAS9-97005 and NASA grant PWC 111-30-40-97.

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Correspondence to V. A. Castro.

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Castro, V., Thrasher, A., Healy, M. et al. Microbial Characterization during the Early Habitation of the International Space Station . Microb Ecol 47, 119–126 (2004).

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  • International Space Station
  • Sphingomonas
  • Space Shuttle
  • Airborne Bacterium
  • Water Port