Microbiological investigations in space experiment TEST
Abstract
Starting in 2010, systematic sampling of fine sediments from the outer surface of the ISS Russian Segment orbiting at the altitude of 400 km has been performed as part of Russian space experiment TEST. In the space vacuum, the samples were sealed in sterile containers and returned to Earth for chemical analysis and detection of viable microbial spores. Over the period from 2010 to 2018, 23 samples were gathered by cosmonauts during their walk-outs on to the ISS surface. Since the beginning of SE TEST, viable units of spore bacteria and fungi have been detected in about 50% samples. One sample contained spore microorganisms, and also a consortium of non-spore-forming bacteria that included radiation-resistant Deinococcus aerolatus. To answer the question about origin of microbial contaminants on the ISS external surfaces, four bacterized Test-Exhibit devices were carried out of the ISS laced in 2017 with the purpose of unprotected exposure of microorganisms to the open space. The devices were attached to surfaces with different illumination and orientation relative to velocity vector for exposure periods of 1 to 2 years. Analyzed were both viable Bacillus pumilus and Aureobasidium pullulans isolated earlier in experiment TEST, and museum archae Methanosarcina- mazei S-6T VKM B-1636T sp. as a standard. Examination of microorganisms returned to Earth in 2018-2019 after 2 years of exposure witnessed to their viability. Comparative analysis of microbial genome fragments before and after exposure in open space was performed using BLAST software. No significant changes were detected by the 16S RNA sequence analysis of bacterial gene fragments and houskeeping genes. Investigation of changes in fungal strains is under way. The high surviving rate of exposed microorganisms proves their resistance to the near-Earth space environment. As such, these microorganisms are able to withstand hard cosmic radiation. These findings can be used as a powerful argument for existence of terrestrial extremophiles that are highly resistant to the open space factors. The established presence of an environment around the ISS is important for augmenting the resistance testing of surface materials and making technical decisions to ensure safety of orbital stations. These most interesting scientific data from the Russian SE TEST demonstrate convincingly the opportunities for using the ISS as a unique platform for researches in the domains of exobiology and planetary protection.
- Publication:
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43rd COSPAR Scientific Assembly. Held 28 January - 4 February
- Pub Date:
- January 2021
- Bibcode:
- 2021cosp...43E2262D