Microbial Monitoring in the International Space Station and Its Application on Earth.

The space habitat is a confined environment with a simple ecosystem that consists mainly of microorganisms and humans. Changes in the pathogenicity and virulence of bacteria, as well as in astronauts' immune systems, during spaceflight may pose potential hazards to crew health. To ensure microbiological safety in the space habitat, a comprehensive analysis of environmental microbiota is needed to understand the overall microbial world in this habitat. The resulting data contribute to evidence-based microbial monitoring, and continuous microbial monitoring will provide information regarding changes in bioburden and microbial ecosystem; this information is indispensable for microbiological management. Importantly, the majority of microbes in the environment are difficult to culture under conventional culture conditions. To improve understanding of the microbial community in the space habitat, culture-independent approaches are required. Furthermore, there is a need to assess the bioburden and physiological activity of microbes during future long-term space habitation, so that the "alert" and/or "action" level can be assessed based on real-time changes in the microbial ecosystem. Here, we review the microbial monitoring in the International Space Station-Kibo, and discuss how these results will be adapted to the microbial control in space habitation and pharmaceutical and food processing industries.