Siems Katharina, Runzheimer Katharina, Rehm Anna, Schwengers Oliver, Heidler von Heilborn David, Kaser Liv, Arndt Franca, Neidhöfer Claudio, Mengel Jan Philipp, Parcina Marijo, Lipski André, Hain Torsten, Moeller Ralf
Department of Radiation Biology, Institute of Aerospace Medicine, German Aerospace Center (DLR), Cologne, Germany.
Department of Bioinformatics and Systems Biology, Justus Liebig University Giessen, Giessen, Germany.
Front Microbiol. 2022 Nov 3;13:1007143. doi: 10.3389/fmicb.2022.1007143. eCollection 2022.
Previous studies have reported that spaceflight specific conditions such as microgravity lead to changes in bacterial physiology and resistance behavior including increased expression of virulence factors, enhanced biofilm formation and decreased susceptibility to antibiotics. To assess if spaceflight induced physiological changes can manifest in human-associated bacteria, we compared three spaceflight relevant isolates (DSM 111179, ISS; DSM 31028, clean room; DSM 113836; artificial gravity bedrest study) with the type strain (DSM 20326). We tested the three strains regarding growth, colony morphology, metabolism, fatty acid and polar lipid pattern, biofilm formation, susceptibility to antibiotics and survival in different stress conditions such as treatment with hydrogen peroxide, exposure to desiccation, and irradiation with X-rays and UV-C. Moreover, we sequenced, assembled, and analyzed the genomes of all four strains. Potential genetic determinants for phenotypic differences were investigated by comparative genomics. We found that all four strains show similar metabolic patterns and the same susceptibility to antibiotics. All four strains were considered resistant to fosfomycin. Physiological differences were mainly observed compared to the type strain and minor differences among the other three strains. The ISS isolate and the bedrest study isolate exhibit a strong delayed yellow pigmentation, which is absent in the other two strains. Pigments were extracted and analyzed by UV/Vis spectroscopy showing characteristic carotenoid spectra. The ISS isolate showed the highest growth rate as well as weighted average melting temperature (WAMT) of fatty acids (41.8°C) of all strains. The clean room isolate showed strongest biofilm formation and a high tolerance to desiccation. In general, all strains survived desiccation better in absence of oxygen. There were no differences among the strains regarding radiation tolerance. Phenotypic and genomic differences among the strains observed in this study are not inevitably indicating an increased virulence of the spaceflight isolate. However, the increased growth rate, higher WAMT and colony pigmentation of the spaceflight isolate are relevant phenotypes that require further research within the human spaceflight context. We conclude that combining genetic analysis with classical microbiological methods allows the detailed assessment of the potential threat of bacteria in highly regulated and extreme environments such as spaceflight environments.
先前的研究报道，太空飞行的特定条件，如微重力，会导致细菌生理和耐药行为发生变化，包括毒力因子表达增加、生物膜形成增强以及对抗生素的敏感性降低。为了评估太空飞行诱导的生理变化是否会在与人类相关的细菌中表现出来，我们将三种与太空飞行相关的菌株（DSM 111179，国际空间站；DSM 31028，洁净室；DSM 113836；人工重力卧床研究）与模式菌株（DSM 20326）进行了比较。我们测试了这三种菌株在生长、菌落形态、代谢、脂肪酸和极性脂质模式、生物膜形成、对抗生素的敏感性以及在不同应激条件下的存活情况，如用过氧化氢处理、暴露于干燥环境以及用X射线和紫外线-C照射。此外，我们对所有四种菌株的基因组进行了测序、组装和分析。通过比较基因组学研究了表型差异的潜在遗传决定因素。我们发现所有四种菌株都表现出相似的代谢模式和相同的抗生素敏感性。所有四种菌株都被认为对磷霉素耐药。与模式菌株相比，主要观察到生理差异，而其他三种菌株之间的差异较小。国际空间站分离株和卧床研究分离株表现出强烈的延迟黄色色素沉着，而其他两种菌株则没有。提取色素并用紫外/可见光谱分析，显示出特征性的类胡萝卜素光谱。国际空间站分离株在所有菌株中显示出最高的生长速率以及脂肪酸的加权平均熔点温度（WAMT）（41.8°C）。洁净室分离株表现出最强的生物膜形成能力和对干燥的高耐受性。一般来说，所有菌株在无氧条件下对干燥的耐受性更好。在辐射耐受性方面，菌株之间没有差异。本研究中观察到的菌株之间的表型和基因组差异并不必然表明太空飞行分离株的毒力增加。然而，太空飞行分离株的生长速率增加、较高的WAMT和菌落色素沉着是相关表型，需要在人类太空飞行背景下进一步研究。我们得出结论，将遗传分析与经典微生物学方法相结合，可以详细评估细菌在高度受控和极端环境（如太空飞行环境）中的潜在威胁。
