Biotechnology and Planetary Protection Group, Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Dr., M/S 89-2, Pasadena, CA, 91109, USA.
Department of Pharmacology and Pharmaceutical Sciences, School of Pharmacy, University of Southern California, Los Angeles, CA, 90089, USA.
Microbiome. 2017 Jul 11;5(1):62. doi: 10.1186/s40168-017-0280-8.
An inflatable lunar/Mars analog habitat (ILMAH), simulated closed system isolated by HEPA filtration, mimics International Space Station (ISS) conditions and future human habitation on other planets except for the exchange of air between outdoor and indoor environments. The ILMAH was primarily commissioned to measure physiological, psychological, and immunological characteristics of human inhabiting in isolation, but it was also available for other studies such as examining its microbiological aspects. Characterizing and understanding possible changes and succession of fungal species is of high importance since fungi are not only hazardous to inhabitants but also deteriorate the habitats. Observing the mycobiome changes in the presence of human will enable developing appropriate countermeasures with reference to crew health in a future closed habitat.
Succession of fungi was characterized utilizing both traditional and state-of-the-art molecular techniques during the 30-day human occupation of the ILMAH. Surface samples were collected at various time points and locations to observe both the total and viable fungal populations of common environmental and opportunistic pathogenic species. To estimate the cultivable fungal population, potato dextrose agar plate counts method was utilized. The internal transcribed spacer region-based iTag Illumina sequencing was employed to measure the community structure and fluctuation of the mycobiome over time in various locations. Treatment of samples with propidium monoazide (PMA; a DNA intercalating dye for selective detection of viable microbial populations) had a significant effect on the microbial diversity compared to non-PMA-treated samples. Statistical analysis confirmed that viable fungal community structure changed (increase in diversity and decrease in fungal burden) over the occupation time. Samples collected at day 20 showed distinct fungal profiles from samples collected at any other time point (before or after). Viable fungal families like Davidiellaceae, Teratosphaeriaceae, Pleosporales, and Pleosporaceae were shown to increase during the occupation time.
The results of this study revealed that the overall fungal diversity in the closed habitat changed during human presence; therefore, it is crucial to properly maintain a closed habitat to preserve it from deteriorating and keep it safe for its inhabitants. Differences in community profiles were observed when statistically treated, especially of the mycobiome of samples collected at day 20. On a genus level Epiccocum, Alternaria, Pleosporales, Davidiella, and Cryptococcus showed increased abundance over the occupation time.
充气式月球/火星模拟栖息地（ILMAH）通过高效微粒空气过滤器模拟国际空间站（ISS）的封闭系统，模拟除了室外和室内环境之间的空气交换之外的其他行星上的人类居住环境。ILMAH 的主要任务是测量人类在隔离状态下的生理、心理和免疫学特征，但它也可用于其他研究，例如检查其微生物学方面。描述和了解真菌物种可能发生的变化和演替非常重要，因为真菌不仅对居住者有害，而且还会使栖息地恶化。观察人类存在时的真菌群落变化，将有助于在未来的封闭栖息地中针对机组人员健康制定适当的对策。
在 ILMAH 中人类居住 30 天后，利用传统和最先进的分子技术对真菌的演替进行了描述。在不同的时间点和位置收集表面样本，以观察常见环境和机会性病原体真菌的总真菌和活菌种群。为了估计可培养真菌种群，使用了土豆葡萄糖琼脂平板计数法。利用基于内部转录间隔区的 iTag Illumina 测序来测量各个位置随时间推移的微生物群落结构和波动。与未用 PMA 处理的样本相比，用吖啶单甲醚（PMA；一种用于选择性检测活菌群的 DNA 嵌入染料）处理样品对微生物多样性有显著影响。统计分析证实，可培养真菌群落结构在居住期间发生了变化（多样性增加，真菌负担减少）。与在任何其他时间点（居住前后）收集的样本相比，在第 20 天收集的样本显示出明显不同的真菌特征。在居住期间，像 Davidiellaceae、Teratosphaeriaceae、Pleosporales 和 Pleosporaceae 这样的可培养真菌家族数量增加。
本研究结果表明，人类存在期间，封闭栖息地中的整体真菌多样性发生了变化；因此，妥善维护封闭栖息地至关重要，以防止其恶化，并确保其居住者的安全。当进行统计处理时，观察到群落图谱的差异，特别是在第 20 天收集的样本的微生物图谱上。在属水平上，Epiccocum、Alternaria、Pleosporales、Davidia 和 Cryptococcus 的丰度在居住期间增加。
