Experimental design and environmental parameters affect Rhodospirillum rubrum S1H response to space flight.

In view of long-haul space exploration missions, the European Space Agency initiated the Micro-Ecological Life Support System Alternative (MELiSSA) project targeting the total recycling of organic waste produced by the astronauts into oxygen, water and food using a loop of bacterial and higher plant bioreactors. In that purpose, the alpha-proteobacterium, Rhodospirillum rubrum S1H, was sent twice to the International Space Station and was analyzed post-flight using a newly developed R. rubrum whole genome oligonucleotide microarray and high throughput gel-free proteomics with Isotope-Coded Protein Label technology. Moreover, in an effort to identify a specific response of R. rubrum S1H to space flight, simulation of microgravity and space-ionizing radiation were performed on Earth under identical culture set-up and growth conditions as encountered during the actual space journeys. Transcriptomic and proteomic data were integrated and permitted to put forward the importance of medium composition and culture set-up on the response of the bacterium to space flight-related environmental conditions. In addition, we showed for the first time that a low dose of ionizing radiation (2 mGy) can induce a significant response at the transcriptomic level, although no change in cell viability and only a few significant differentially expressed proteins were observed. From the MELiSSA perspective, we could argue the effect of microgravity to be minimized, whereas R. rubrum S1H could be more sensitive to ionizing radiation during long-term space exploration mission.

针对长距离太空探索任务，欧洲空间局（European Space Agency）启动了微生态生命支持系统替代方案（Micro-Ecological Life Support System Alternative，MELiSSA）项目，旨在通过细菌与高等植物生物反应器闭环系统，将宇航员产生的有机废物完全循环转化为氧气、水与食物。为此，研究人员将α-变形菌纲（alpha-proteobacterium）的深红螺菌（Rhodospirillum rubrum）S1H两次送往国际空间站，并借助全新开发的深红螺菌全基因组寡核苷酸微阵列，以及搭载同位素编码蛋白标记（Isotope-Coded Protein Label）技术的高通量无凝胶蛋白质组学技术，对飞行后的菌株开展分析。此外，为明确深红螺菌S1H对太空飞行的特异性响应，研究人员在地球环境中模拟微重力与太空电离辐射条件，采用与实际太空任务完全一致的培养设置与生长参数开展实验。研究人员整合转录组与蛋白质组数据后证实，培养基组分与培养设置对该菌株应对太空飞行相关环境条件的响应具有关键影响。此外，本研究首次证实，低剂量电离辐射（2毫戈瑞，2 mGy）可在转录组层面引发显著响应——尽管此时细胞存活率未发生变化，且仅观测到少量显著差异表达的蛋白质。从MELiSSA项目的视角来看，微重力的影响可被最小化，而在长周期太空探索任务中，深红螺菌S1H对电离辐射可能更为敏感。