The gut microbiota plays a significant role in a variety of host behavioral and physiological processes. The mechanisms by which the gut microbiota and the host communicate are not fully resolved but include both humoral and direct neural signals. The composition of the microbiota is affected by internal (host) factors and external (environmental) factors. One such signal is photoperiod, which is represented endogenously by nocturnal pineal melatonin (MEL) secretion. Removal of the MEL signal via pinealectomy abolishes many seasonal responses to photoperiod. In Siberian hamsters (Phodopus sungorus), MEL drives robust seasonal shifts in physiology and behavior, such as immunity, stress, body mass, and aggression. While the profile of the gut microbiota also changes by season, it is unclear whether these changes are driven by pineal signals. We hypothesized that the pineal gland mediates seasonal alterations in the composition of the gut microbiota. To test this, we placed pinealectomized and intact hamsters into long or short photoperiods for 8 weeks, collected weekly fecal samples, and measured weekly food intake, testis volume, and body mass. We determined microbiota composition using 16S rRNA sequencing (Illumina MiSeq). We found significant effects of treatment and time on the abundances of numerous bacterial genera. We also found significant associations between individual OTU abundances and body mass, testis mass, and food intake, respectively. Finally, results indicate a relationship between overall community structure, and body and testis masses. These results firmly establish a role for the pineal gland in mediating seasonal alterations in the gut microbiota. Further, these results identify a novel neuroendocrine pathway by which a host regulates seasonal shifts in gut community composition, and indicates a relationship between seasonal changes in the gut microbiota and seasonal physiological adjustments.

中文翻译：

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松果体的新作用：调节西伯利亚仓鼠肠道微生物群的季节性变化。

肠道微生物群在多种宿主行为和生理过程中发挥着重要作用。肠道微生物群和宿主交流的机制尚未完全解决，但包括体液和直接神经信号。微生物群的组成受内部（宿主）因素和外部（环境）因素的影响。一种这样的信号是光周期，它是由夜间松果体褪黑激素 (MEL) 分泌的内源性代表。通过松果体切除术去除 MEL 信号消除了对光周期的许多季节性反应。在西伯利亚仓鼠 ( Phodopus sungorus)，MEL 推动生理和行为的强烈季节性变化，例如免疫、压力、体重和攻击性。虽然肠道微生物群的特征也会随季节变化，但尚不清楚这些变化是否由松果体信号驱动。我们假设松果体介导了肠道微生物群组成的季节性变化。为了测试这一点，我们将松果体切除的完整仓鼠置于长光周期或短光周期中 8 周，每周收集粪便样本，并测量每周的食物摄入量、睾丸体积和体重。我们使用 16S rRNA 测序 (Illumina MiSeq) 确定微生物群组成。我们发现处理和时间对众多细菌属的丰度有显着影响。我们还发现个体 OTU 丰度与体重、睾丸质量和食物摄入量之间存在显着关联，分别。最后，结果表明整体群落结构与身体和睾丸质量之间存在关系。这些结果牢固地确立了松果体在调节肠道微生物群季节性变化中的作用。此外，这些结果确定了一种新的神经内分泌途径，宿主通过该途径调节肠道群落组成的季节性变化，并表明肠道微生物群的季节性变化与季节性生理调整之间存在关系。