Reduced gravity, or microgravity, can have a pronounced impact on the physiology of animals, but the effects on their associated microbiomes are not well understood. Here, the impact of modeled microgravity on the shedding of Gram-negative lipopolysaccharides (LPS) by the symbiotic bacterium Vibrio fischeri was examined using high-aspect ratio vessels. LPS from V. fischeri is known to induce developmental apoptosis within its symbiotic tissues, which is accelerated under modeled microgravity conditions. In this study, we provide evidence that exposure to modeled microgravity increases the amount of LPS released by the bacterial symbiont in vitro. The higher rates of shedding under modeled microgravity conditions are associated with increased production of outer-membrane vesicles (OMV), which has been previously correlated to flagellar motility. Mutants of V. fischeri defective in the production and rotation of their flagella show significant decreases in LPS shedding in all treatments, but levels of LPS are higher under modeled microgravity despite loss of motility. Modeled microgravity also appears to affect the outer-membrane integrity of V. fischeri, as cells incubated under modeled microgravity conditions are more susceptible to cell-membrane-disrupting agents. These results suggest that, like their animal hosts, the physiology of symbiotic microbes can be altered under microgravity-like conditions, which may have important implications for host health during spaceflight.

重力降低或微重力可能会对动物的生理产生显着影响，但对其相关微生物群的影响尚不十分清楚。在这里，使用高长宽比的容器检查了微重力对共生细菌费氏弧菌对革兰氏阴性脂多糖（LPS）脱落的影响。V. fischeri的LPS已知其诱导其共生组织内的发育凋亡，其在模拟微重力条件下被加速。在这项研究中，我们提供证据表明暴露于模型微重力会增加细菌共生体在体外释放的LPS量。在模拟微重力条件下，较高的脱落速率与外膜囊泡（OMV）的产量增加有关，后者以前与鞭毛运动有关。在所有处理中，在鞭毛产生和旋转中有缺陷的费氏弧菌突变体均表现出LPS脱落的显着降低，但是在模拟微重力作用下，LPS的水平更高，尽管丧失了运动能力。模拟微重力也似乎影响的外膜完整性五鲵，因为在模拟微重力条件下孵育的细胞更容易受到细胞膜破坏剂的影响。这些结果表明，就像它们的动物宿主一样，共生微生物的生理学可以在类似微重力的条件下发生变化，这可能对航天飞行中宿主的健康产生重要影响。