Extreme factors such as space microgravity, radiation, and magnetic field differ from those that occur on Earth. Microgravity may induce and select some microorganisms for physiological, metabolic, and/or genetic variations. This study was conducted to determine the effects of simulated microgravity conditions on the metabolism and gene expression of the probiotic bacterium Lactobacillus reuteri DSM17938. To investigate microbial response to simulated microgravity, two devices-the rotating wall vessel (RWV) and the random positioning machine (RPM)-were used. Microbial growth, reuterin production, and resistance to gastrointestinal passage were assessed, and morphological characteristics were analyzed by scanning electron microscopy. The expression of some selected genes that are responsive to stress conditions and to bile salts stress was evaluated through real-time quantitative polymerase chain reaction assay. Monitoring of bacterial growth, cell size, and shape under simulated microgravity did not reveal differences compared with 1 × g controls. On the contrary, an enhanced production of reuterin and a greater tolerance to the gastrointestinal passage were observed. Moreover, some stress genes were upregulated under RWV conditions, especially after 24 h of treatment, whereas RPM conditions seemed to determine a downregulation over time of the same stress genes. These results show that simulated microgravity could alter some physiological characteristics of L. reuteri DSM17938 with regard to tolerance toward stress conditions encountered on space missions and could be useful to elucidate the adaptation mechanisms of microbes to the space environment.

中文翻译：

---

在两个模拟微重力系统下，路透乳杆菌DSM17938的生长：路透素生产，胃肠道抗性和应激基因表达响应的变化。

空间微重力，辐射和磁场等极端因素与地球上发生的因素不同。微重力可能会诱导并选择一些微生物进行生理，代谢和/或遗传变异。进行这项研究是为了确定模拟微重力条件对益生菌罗伊氏乳杆菌DSM17938的代谢和基因表达的影响。为了研究微生物对模拟微重力的响应，使用了两种设备-旋转壁容器（RWV）和随机定位机（RPM）。评估微生物的生长，路透菌素的产生和对胃肠道的抵抗力，并通过扫描电子显微镜分析其形态特征。通过实时定量聚合酶链反应分析评估了一些对压力条件和胆盐压力有反应的选定基因的表达。与1×g对照相比，在模拟微重力下监测细菌的生长，细胞大小和形状没有发现差异。相反，观察到路透菌素的产量增加和对胃肠道的耐受性增强。此外，一些应激基因在RWV条件下，特别是在治疗24小时后，被上调，而RPM条件似乎决定了相同应激基因随时间的下调。这些结果表明，模拟微重力可能会改变L的某些生理特性。