For potential future human missions to the Moon or Mars and sustained presence in the International Space Station, a safe enclosed habitat environment for astronauts is required. Potential microbial contamination of closed habitats presents a risk for crewmembers due to reduced human immune response during long-term confinement. To make future habitat designs safer for crewmembers, lessons learned from characterizing analogous habitats is very critical. One of the key issues is that how human presence influences the accumulation of microorganisms in the closed habitat. Molecular technologies, along with traditional microbiological methods, were utilized to catalog microbial succession during a 30-day human occupation of a simulated inflatable lunar/Mars habitat. Surface samples were collected at different time points to capture the complete spectrum of viable and potential opportunistic pathogenic bacterial population. Traditional cultivation, propidium monoazide (PMA)-quantitative polymerase chain reaction (qPCR), and adenosine triphosphate (ATP) assays were employed to estimate the cultivable, viable, and metabolically active microbial population, respectively. Next-generation sequencing was used to elucidate the microbial dynamics and community profiles at different locations of the habitat during varying time points. Statistical analyses confirm that occupation time has a strong influence on bacterial community profiles. The Day 0 samples (before human occupation) have a very different microbial diversity compared to the later three time points. Members of Proteobacteria (esp. Oxalobacteraceae and Caulobacteraceae) and Firmicutes (esp. Bacillaceae) were most abundant before human occupation (Day 0), while other members of Firmicutes (Clostridiales) and Actinobacteria (esp. Corynebacteriaceae) were abundant during the 30-day occupation. Treatment of samples with PMA (a DNA-intercalating dye for selective detection of viable microbial population) had a significant effect on the microbial diversity compared to non-PMA-treated samples. Statistical analyses revealed a significant difference in community structure of samples over time, particularly of the bacteriomes existing before human occupation of the habitat (Day 0 sampling) and after occupation (Day 13, Day 20, and Day 30 samplings). Actinobacteria (mainly Corynebacteriaceae) and Firmicutes (mainly Clostridiales Incertae Sedis XI and Staphylococcaceae) were shown to increase over the occupation time period. The results of this study revealed a strong relationship between human presence and succession of microbial diversity in a closed habitat. Consequently, it is necessary to develop methods and tools for effective maintenance of a closed system to enable safe human habitation in enclosed environments on Earth and beyond.
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机译：对于潜在未来的人类任务到月球或火星和国际空间站的持续存在，需要为宇航员提供安全的栖息地环境。由于在长期限制期间减少人类免疫应答，闭孔栖息地的潜在微生物污染造成了船员的风险。为了使未来的栖息地设计更安全，为船员来说，来自表征类似栖息地的教训非常关键。关键问题之一是人类存在如何影响闭合栖息地的微生物的积累。分子技术以及传统的微生物方法，用于在30天的人类占用模拟充气月/火星栖息地期间对微生物连续的微生物连续。在不同的时间点收集表面样品，以捕获可行性和潜在的机会致病细菌种群的完整光谱。使用传统培养，单氮化物（PMA） - 定量聚合酶链反应（QPCR）和三磷酸腺苷（ATP）测定分别估计可培养，可行和代谢活性的微生物群体。在不同时间点期间，使用下一代测序阐明在栖息地的不同位置处的微生物动力学和社区谱。统计分析证实，占用时间对细菌群落概况产生了强烈影响。与后期三个时间点相比，第0天样本（在人职业之前）具有非常不同的微生物分集。植物的成员（ESP。Oxalobacteraceae和花梗）和压缩（ESP.Bacillaceae）在人类职业（第0天）之前最丰富，而其他成员（梭菌）和Actinobacteria（尤其是棒状易氧基金）在30天内丰富职业。与非PMA处理的样品相比，用PMA（用于选择性微生物群体的DNA嵌入染料的DNA嵌入染料）对微生物多样性具有显着影响。统计学分析显示样品的群落结构随着时间的推移，特别是人类居住前（第0天采样）和职业（第13天，第20天和第30天的应用）存在的菌株的显着差异。 actinobacteria（主要是棒状细菌）和骨灰（主要是Clostridales Incertae Sedis xi和葡萄球菌），在占用时间内增加。该研究的结果揭示了人类存在与闭合栖息地的微生物多样性的良好关系。因此，有必要开发用于有效维护封闭系统的方法和工具，以便在地球及以外的封闭环境中实现安全的人类居住。
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