Abstract: The degradation of grasslands caused by overgrazing provides abundant protein food resources for the plateau pika (Ochotona curzoniae) and changes in the content of essential amino acids (especially methionine) in the food can affect the host intestinal microbial community. In this study, plateau pikas were fed with 0. 26% and 0. 45% methionine diets according to the methionine content in their stomach contents in different degraded grasslands for 50 days. Collected feces were used for metagenomics and non-targeted metabolomics analysis to evaluate the effects of high methionine treatment on intestinal microbial communities and metabolites of plateau pika. The results showed that there was no significant difference in the α and β diversity of the intestinal microbial community of plateau pikas in the high methionine group compared with the low methionine group, but the abundance of Candidatus_Saccharibacteria and Tenericutes was significantly increased and the functions of butyric acid metabolism, taurine, and hypotaurine metabolism were significantly expressed, and the up-regulated metabolites were mainly enriched in primary bile acid synthesis, ascorbic acid and aldehyde metabolism, Th17 cell differentiation, taurine and hypotaurine metabolism, B cell receptor signaling pathway, T cell receptor signaling pathway, and NF-κB pathway. On the other hand, the carbohydrate metabolism function of plateau pika microbiota in the low methionine group was significantly expressed, and its up-regulated metabolites were mainly enriched in amino acid metabolism-related pathways. These results suggest that high methionine foods can change intestinal microbes and their metabolites, which may enhance the immune and reproductive performance of the host, and play an important role in improving the individual fitness and population size of plateau pikas.

Key words: Plateau pika (Ochotona curzoniae), Methionine, Gut microbes, Metagenomics, Non-targeted metabolomics

摘要： 过度放牧引起的退化草地为高原鼠兔(Ochotona curzoniae)提供了丰富的蛋白质食物资源，而食物中必需氨基酸(尤其是蛋氨酸)含量的变化会影响宿主体内肠道微生物群落。本研究依据不同退化草地高原鼠兔胃内容物中的蛋氨酸含量，使用0.26%和0.45%蛋氨酸含量的兔颗粒饲料分组饲喂高原鼠兔，50 d后收集粪便，利用宏基因组学以及非靶向代谢组学分析，评估高蛋氨酸处理对高原鼠兔肠道微生物群落及其代谢产物的影响。结果表明，与低蛋氨酸组相比，高蛋氨酸组高原鼠兔肠道微生物群落的α、β多样性均无显著差异，但Candidatus_Saccharibacteria、软壁菌门(Tenericutes)等菌群的丰度显著增加，丁酸代谢、牛磺酸和次牛磺酸代谢等菌群功能显著表达，其上调的代谢产物主要在初级胆汁酸合成、抗坏血酸和醛酸代谢、Th17细胞分化、牛磺酸和次牛磺酸代谢、B细胞受体信号通路、T细胞受体信号通路、NF-κB途径等通路富集；而低蛋氨酸组高原鼠兔菌群的糖类代谢功能显著表达，其上调的代谢产物主要在氨基酸代谢相关通路富集。上述结果表明，高蛋氨酸食物可改变高原鼠兔肠道微生物及其代谢产物，进而可能增强宿主的免疫和繁殖性能，对提高高原鼠兔个体适合度及其种群数量有重要的作用。

关键词: 高原鼠兔, 蛋氨酸, 肠道微生物, 宏基因组学, 非靶向代谢组学