Characterization and monitoring of microbes in the International Space Station drinking water

摘要

This study focuses on the development of procedures to characterize the microbial quality of International Space Station (ISS) and shuttle drinking water at various stages of water treatment. In addition to traditional culture-based techniques, ATP, endotoxin, and DNA targeted microbial enumeration procedures were employed to elucidate the microbial contamination of the ISS drinking water. Drinking water processed at various stages for the STS-113 mission aboard the Endeavor OV-105 shuttle, as well as aboard the ISS, was sampled and examined for microbial contamination using state-of-the-art quantitative and qualitative methodologies. Biomolecule-targeted microbial detection methods revealed the presence of non-cultivable microbes in the drinking water, and confirmed the fact that the measures taken to cultivate microbes from the drinking water samples were estimating only 10% of the microbial contamination. Both culture and DNA-based methodologies reported the presence of Acidovorax temperans, a halogen (biocide) reducing bacterium from the ISS-regenerated water sample. Although the water collected from the drinking water dispenser did not contain any measurable cultivable microbes, the DNA-based procedures retrieved ribosomal sequences of the opportunistic pathogens Afipia, Delftia, Propionibacterium, and Ochrobactrum. The present study did not confirm the presence of active pathogens in the drinking water, although evidence strongly suggests that implementation of new cultivation approaches to identify the presence of pathogens is essential.