Abstract
BackgroundThe International Space Station (ISS) represents a unique biotope for the human crew but also for introduced microorganisms. Microbes experience selective pressures such as microgravity, desiccation, poor nutrient-availability due to cleaning, and an increased radiation level. We hypothesized that the microbial community inside the ISS is modified by adapting to these stresses.For this reason, we analyzed 8–12 years old dust samples from Russian ISS modules with major focus on the long-time surviving portion of the microbial community. We consequently assessed the cultivable microbiota of these samples in order to analyze their extremotolerant potential against desiccation, heat-shock, and clinically relevant antibiotics. In addition, we studied the bacterial and archaeal communities from the stored Russian dust samples via molecular methods (next-generation sequencing, NGS) and compared our new data with previously derived information from the US American ISS dust microbiome.ResultsWe cultivated and identified in total 85 bacterial, non-pathogenic isolates (17 different species) and 1 fungal isolate from the 8–12 year old dust samples collected in the Russian segment of the ISS. Most of these isolates exhibited robust resistance against heat-shock and clinically relevant antibiotics. Microbial 16S rRNA gene and archaeal 16S rRNA gene targeting Next Generation Sequencing showed signatures of human-associated microorganisms (Corynebacterium, Staphylococcus, Coprococcus etc.), but also specifically adapted extremotolerant microorganisms. Besides bacteria, the detection of archaeal signatures in higher abundance was striking.ConclusionsOur findings reveal (i) the occurrence of living, hardy microorganisms in archived Russian ISS dust samples, (ii) a profound resistance capacity of ISS microorganisms against environmental stresses, and (iii) the presence of archaeal signatures on board. In addition, we found indications that the microbial community in the Russian segment dust samples was different to recently reported US American ISS microbiota.Electronic supplementary materialThe online version of this article (doi:10.1186/s40168-016-0217-7) contains supplementary material, which is available to authorized users.
Highlights
The International Space Station (ISS) represents a unique biotope for the human crew and for introduced microorganisms
We hypothesize that the microbial community thriving and surviving inside of the International Space Station becomes adapted to desiccation and other stresses
The retrieved microbial isolates were analyzed with respect to their resistance towards heatshocks and antibiotics
Summary
The International Space Station (ISS) represents a unique biotope for the human crew and for introduced microorganisms. We hypothesized that the microbial community inside the ISS is modified by adapting to these stresses. For this reason, we analyzed 8–12 years old dust samples from Russian ISS modules with major focus on the long-time surviving portion of the microbial community. The ISS microbial community is under constant surveillance to ensure the health of the human crew working on-board, as well as to evaluate potential risk factors for the integrity of the ISS materials and its function. There is particular interest on the response of microbial communities to selective pressures such as microgravity, which could induce severe changes and adaptation processes [10]
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