Ambient temperature (T_a) is an important factor in shaping phenotypic plasticity. Plasticity is generally beneficial for animals in adapting to their environments. Gut microbiota are crucial in regulating host physiological and behavioral processes. However, whether the gut microbiota play a role in regulating host phenotypic plasticity under the conditions of repeated fluctuations in environmental factors has rarely been examined. We used intermittent T_a acclimations to test the hypothesis that the plasticity of gut microbiota confers on the host a metabolic adaptation to T_a fluctuations. Mongolian gerbils (Meriones unguiculatus) were acclimated to intermittent 5°C to 23°C, 37°C to 23°C or 23°C to 23°C conditions for 3 cycles (totally 3 months). Intermittent T_a acclimations induced variations in resting metabolic rate (RMR), serum thyroid hormones, and core body temperature (T_b). We further identified that the β-diversity of the microbial community varied with T_a and showed diverse responses during the 3 cycles. Some specific bacteria were more sensitive to T_a and were associated with host dynamic metabolic plasticity during T_a acclimations. In addition, depletion of gut microbiota in antibiotic-treated gerbils impaired metabolic plasticity, particularly at low T_a, whereas supplementation with propionate as an energy resource improved the inhibited thermogenic capacity and increased the survival rate in the cold. These findings demonstrate that both gut microbiota and their host were more adaptive after repeated acclimations, and dynamic gut microbiota and their metabolites may confer host plasticity in thermoregulation in response to T_a fluctuations. It also implies that low T_a is a crucial cue in driving symbiosis between mammals and their gut microbiota during evolution.

中文翻译：

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肠道微生物群和宿主体温调节对环境温度波动的响应

环境温度 ( T _a ) 是塑造表型可塑性的重要因素。可塑性通常有利于动物适应环境。肠道微生物群在调节宿主生理和行为过程中至关重要。然而，在环境因素反复波动的情况下，肠道微生物群是否在调节宿主表型可塑性方面发挥作用很少被研究。我们使用间歇性T _a适应来测试肠道微生物群的可塑性赋予宿主对T _a波动的代谢适应的假设。蒙古沙鼠（Meriones unguiculatus) 适应间歇性 5°C 至 23°C、37°C​​ 至 23°C 或 23°C 至 23°C 的条件，持续 3 个周期（共 3 个月）。间歇性T _a适应引起静息代谢率 (RMR)、血清甲状腺激素和核心体温 ( T _b ) 的变化。我们进一步确定微生物群落的 β 多样性随T _a变化，并在 3 个循环中表现出不同的反应。一些特定的细菌对T _a更敏感，并且与T _a驯化期间宿主的动态代谢可塑性有关。此外，抗生素处理的沙鼠肠道微生物群的耗竭损害了代谢可塑性，特别是在低T _a，而补充丙酸盐作为能源改善了受抑制的产热能力并增加了寒冷中的存活率。这些发现表明，肠道微生物群及其宿主在反复驯化后更具适应性，动态肠道微生物群及其代谢物可能赋予宿主响应T _a波动的体温调节可塑性。这也意味着低T _a是在进化过程中推动哺乳动物与其肠道微生物群之间共生的关键线索。