Preparing for the crewed Mars journey: microbiota dynamics in the confined Mars500 habitat during simulated Mars flight and landing

摘要

Background: The Mars500 project was conceived as the first full duration simulation of a crewed return flight to Mars.\udFor 520 days, six crew members lived confined in a specifically designed spacecraft mock-up. The herein described\ud“MIcrobial ecology of Confined Habitats and humAn health” (MICHA) experiment was implemented to acquire\udcomprehensive microbiota data from this unique, confined manned habitat, to retrieve important information\udon the occurring microbiota dynamics, the microbial load and diversity in the air and on various surfaces.\udIn total, 360 samples from 20 (9 air, 11 surface) locations were taken at 18 time-points and processed by\udextensive cultivation, PhyloChip and next generation sequencing (NGS) of 16S rRNA gene amplicons.\udResults: Cultivation assays revealed a Staphylococcus and Bacillus-dominated microbial community on various surfaces,\udwith an average microbial load that did not exceed the allowed limits for ISS in-flight requirements indicating adequate\udmaintenance of the facility. Areas with high human activity were identified as hotspots for microbial accumulation.\udDespite substantial fluctuation with respect to microbial diversity and abundance throughout the experiment, the\udlocation within the facility and the confinement duration were identified as factors significantly shaping the microbial\uddiversity and composition, with the crew representing the main source for microbial dispersal. Opportunistic pathogens,\udstress-tolerant or potentially mobile element-bearing microorganisms were predicted to be prevalent throughout the\udconfinement, while the overall microbial diversity dropped significantly over time.\udConclusions: Our findings clearly indicate that under confined conditions, the community structure remains a highly\uddynamic system which adapts to the prevailing habitat and micro-conditions. Since a sterile environment is not\udachievable, these dynamics need to be monitored to avoid spreading of highly resistant or potentially pathogenic\udmicroorganisms and a potentially harmful decrease of microbial diversity. If necessary, countermeasures are required,\udto maintain a healthy, diverse balance of beneficial, neutral and opportunistic pathogenic microorganisms. Our results\udserve as an important data collection for (i) future risk estimations of crewed space flight, (ii) an optimized design and\udplanning of a spacecraft mission and (iii) for the selection of appropriate microbial monitoring approaches and potential\udcountermeasures, to ensure a microbiologically safe space-flight environment.