MICROBIAL CHARACTERIZATION OF POTABLE WATER AND ATMOSPHERIC CONDENSATE OF THE RUSSIAN SEGMENT OF THE INTERNATIONAL SPACE STATION

The paper presents an investigation of the taxonomic composition of cultivable heterotrophic bacteria in potable water and atmospheric condensate in the Russian segment of the International space station (ISS RS), and resistance of the most commonly occurring species to high concentrations of silver ions and heating. Water samples collected on the stages of pre-launch treatment contained 3 species of nonpathogenic bacteria, their total number did not exceed 200 CFU/ml. Acidovorax temperans prevailed in all samples. Taxonomic composition of bacteria in the water storage tank SVO-ZV included 6 species. A. temperans and Cupriavidus metallidurans were the most occurring species. The second is adapted to survive several forms of heavy metal stress, including silver. The largest number of microorganisms was detected in the AC sample (1.1 × 105 CFU/ml). The sample contained 9 species; the most numerous were Ralstonia insidiosa and C. metallidurans. All tested A. temperans isolates demonstrated resistance to high silver ions concentrations. Resistance was observed even in solutions with silver concentrations of 10 and 20 mg/l equal to and exceeding twofold silver concentration in the ISS RS disinfectant solution for potable water regenerated from condensate. To eliminate the silver-resistant strains, additional water sterilization can be performed by heating at 70 °С over 30 minutes.