Radiation Biology Department, Institute of Aerospace Medicine, German Aerospace Center e.V. (DLR), Linder Höhe, 51147, Cologne, Germany.
Institute for Microbiology, University of Regensburg, Universitaetsstrasse 31, 93053, Regensburg, Germany.
Microbiome. 2017 Oct 4;5(1):129. doi: 10.1186/s40168-017-0345-8.
The Mars500 project was conceived as the first full duration simulation of a crewed return flight to Mars. For 520 days, six crew members lived confined in a specifically designed spacecraft mock-up. The herein described "MIcrobial ecology of Confined Habitats and humAn health" (MICHA) experiment was implemented to acquire comprehensive microbiota data from this unique, confined manned habitat, to retrieve important information on the occurring microbiota dynamics, the microbial load and diversity in the air and on various surfaces. In total, 360 samples from 20 (9 air, 11 surface) locations were taken at 18 time-points and processed by extensive cultivation, PhyloChip and next generation sequencing (NGS) of 16S rRNA gene amplicons.
Cultivation assays revealed a Staphylococcus and Bacillus-dominated microbial community on various surfaces, with an average microbial load that did not exceed the allowed limits for ISS in-flight requirements indicating adequate maintenance of the facility. Areas with high human activity were identified as hotspots for microbial accumulation. Despite substantial fluctuation with respect to microbial diversity and abundance throughout the experiment, the location within the facility and the confinement duration were identified as factors significantly shaping the microbial diversity and composition, with the crew representing the main source for microbial dispersal. Opportunistic pathogens, stress-tolerant or potentially mobile element-bearing microorganisms were predicted to be prevalent throughout the confinement, while the overall microbial diversity dropped significantly over time.
Our findings clearly indicate that under confined conditions, the community structure remains a highly dynamic system which adapts to the prevailing habitat and micro-conditions. Since a sterile environment is not achievable, these dynamics need to be monitored to avoid spreading of highly resistant or potentially pathogenic microorganisms and a potentially harmful decrease of microbial diversity. If necessary, countermeasures are required, to maintain a healthy, diverse balance of beneficial, neutral and opportunistic pathogenic microorganisms. Our results serve as an important data collection for (i) future risk estimations of crewed space flight, (ii) an optimized design and planning of a spacecraft mission and (iii) for the selection of appropriate microbial monitoring approaches and potential countermeasures, to ensure a microbiologically safe space-flight environment.
火星 500 项目的构想是首次对载人返回火星的全程模拟。在 520 天的时间里，六名机组人员被限制在一个专门设计的航天器模型中生活。本文所述的“密闭环境中的微生物生态学和人类健康”（MICHA）实验旨在从这个独特的、密闭的载人栖息地获取全面的微生物数据，以获取关于发生的微生物动态、空气中和各种表面上的微生物负荷和多样性的重要信息。总共从 20 个（9 个空气，11 个表面）位置采集了 360 个样本，在 18 个时间点进行处理，并通过广泛的培养、PhyloChip 和 16S rRNA 基因扩增子的下一代测序（NGS）进行处理。
培养分析显示，各种表面上的微生物群落以葡萄球菌和芽孢杆菌为主，平均微生物负荷未超过国际空间站飞行要求的允许限度，表明设施得到了充分的维护。高人类活动区域被确定为微生物积累的热点。尽管整个实验过程中微生物多样性和丰度都有很大的波动，但设施内的位置和隔离时间被确定为显著影响微生物多样性和组成的因素，机组人员是微生物传播的主要来源。预计机会性病原体、耐应激或可能具有移动元件的微生物在整个隔离期间普遍存在，而微生物多样性总体上随着时间的推移显著下降。
我们的研究结果清楚地表明，在密闭条件下，群落结构仍然是一个高度动态的系统，它适应于流行的栖息地和微环境。由于无法实现无菌环境，因此需要对这些动态进行监测，以避免传播高度耐药或潜在的致病性微生物，以及微生物多样性的潜在有害下降。如果有必要，需要采取对策，以维持有益、中性和机会性病原体的有益、多样的平衡。我们的研究结果为（i）载人航天飞行的风险评估、（ii）航天器任务的优化设计和规划以及（iii）选择适当的微生物监测方法和潜在对策提供了重要的数据收集，以确保微生物安全的太空飞行环境。
