Microbial Observatory (ISS-MO): Indoor microbiome study of the International Space Station surfaces

Presented here is the environmental microbiome study of the International Space Station surfaces. The environmental samples were collected with the polyester wipes from eight different locations in the ISS during two consecutive sampling sessions (three months apart). The specific objective was to unveil the pool of genes for each location during two separate sessions to learn of functional and metabolic diversity of microorganisms in the ISS. The International Space Station (ISS) as a closed built environment has its own environmental microbiome which is shaped by microgravity, radiation, and limited human presence. The microbial diversity associated with ISS environmental surfaces was investigated during this study. Polyester wipes and contact slides were used for sampling of eight various surface locations on the ISS at different time periods. The samples were retrieved and analyzed immediately upon the return to the Earth (via Soyuz TMA-14M or Dragon capsule from SpaceX). After surface sample collection, contact slides containing nutrient media for the growth of bacteria and fungi were incubated at 25C. The polyester wipes were processed to measure microbial burden (R2A, Blood Agar, and Potato Dextrose Agar) and recover cultivable bacteria as well as fungi. Subsequently, viable microbial burden was assessed using Adenosine Triphosphate (ATP) assay, and quantitative polymerase chain reaction (PCR) methods after propidium monoazide (PMA) treatment. The 16S-tag and metagenome analyses were used to elucidate viable microbial diversity. The cultivable bacterial population yield from the polyester wipes was very high (5 to 7-logs) when compared with the contact slides (10^2 to 10^3 CFU/m2). The PMA-qPCR analysis showed considerable variation of viable bacterial population (10^5 to 10^9 16S rDNA gene copies/m2) among locations sampled. Unlike contact slides, polyester wipes cover much larger sample surface (~1 m2) and produce much more reliable results of the microbial diversity of the ISS covering both cultivable and non-cultivable species. The cultivable, total, and viable microbial diversity was determined utilizing state-of-the art molecular techniques. The implementation of the PMA assay before DNA extraction allowed distinguishing viable microorganisms, which is crucial for determining their role to the crew health, the ISS maintenance and the general knowledge of the closed environmentally controlled built systems.

本报告呈现了国际空间站表面环境的微生物群研究。环境样本采用聚酯擦拭布从国际空间站八个不同地点在连续两次采样（相隔三个月）期间采集。研究的具体目标是在两次分别的采样中揭示每个地点的基因库，以了解国际空间站内微生物的功能和代谢多样性。国际空间站（ISS）作为一个封闭的建造环境，其环境微生物群由微重力、辐射和有限的人类活动塑造。本研究调查了与国际空间站环境表面相关的微生物多样性。聚酯擦拭布和接触玻片被用于在国际空间站不同时间段的八个不同表面位置的采样。样本在返回地球后（通过联盟号TMA-14M或SpaceX的龙飞船）立即被取回并进行分析。表面样本收集后，含有细菌和真菌生长营养介质的接触玻片在25°C下进行孵化。聚酯擦拭布经过处理以测量微生物负荷（R2A、血液琼脂和马铃薯葡萄糖琼脂），以及恢复可培养的细菌和真菌。随后，使用腺苷三磷酸（ATP）试验和经丙啶单氮烷（PMA）处理后的定量聚合酶链式反应（PCR）方法评估了存活的微生物负荷。16S标签和宏基因组分析被用于阐明存活的微生物多样性。与接触玻片相比，聚酯擦拭布覆盖的样本表面面积更大（约1平方米），并且能够产生更可靠的微生物多样性结果，包括可培养和非可培养物种。利用最先进的分子技术确定了可培养的、总的和存活的微生物多样性。在DNA提取前实施PMA试验，允许区分存活的微生物，这对于确定其在机组人员健康、国际空间站维护以及封闭环境控制建造系统一般知识中的角色至关重要。