海拔高度对青藏高原放牧牦牛肠道菌群多样性的影响

Effect of altitude on the diversity of gut microbiota of yaks grazing on the Qinghai-Tibet Plateau

摘要:

【背景】肠道菌群与宿主健康及环境适应性密切相关，牦牛为青藏高原特有的草食性反刍动物，不同海拔高度如何影响牦牛肠道菌群组成及肠道菌群在牦牛适应高海拔生境中的作用尚不清楚。【目的】探究青藏高原放牧牦牛肠道菌群多样性及其与海拔高度间的关系。【方法】采集青海省玛沁县(海拔4 220 m)和乐都县(2 745 m) 2个海拔高度放牧牦牛的22份新鲜粪便样品，然后利用16S rRNA基因通用引物扩增V3-V4区并进行高通量测序和分析。【结果】从22份样品中共获得1 723 018条有效序列，通过聚类共获得1 113个操作分类单元(operational taxonomic unit，OTU)，注释到22个门和263个属。在门和属分类水平上，2组样品中的优势菌为厚壁菌门(Firmicutes)、拟杆菌门(Bacteroidetes)、瘤胃菌科UCG-005菌属(Ruminococcaceae_UCG-005)和理研菌科RC9菌属(Rikenellaceae_RC9_gut_group)，但是其相对丰度在2组样品中差异显著。随着海拔升高，厚壁菌门和瘤胃菌科UCG-005菌属相对丰度显著提高，而拟杆菌门和理研菌科RC9菌属的相对丰度显著降低。对不同样品菌群组成和差异分析表明，放牧牦牛的肠道微生物群落组成受不同海拔环境的影响较大。此外，通过PICRUSt2功能预测分析表明，随着海拔升高，能量代谢、辅因子代谢、维生素代谢、核苷酸代谢、多糖代谢和氨基酸代谢等相关代谢通路显著富集，这可能与牦牛通过提高牧草利用效率并获取更多能量以适应极端高海拔环境有关。【结论】不同海拔环境放牧牦牛的肠道菌群组成具有明显的差异，并且肠道菌群对于牦牛适应高海拔生境具有重要功能。

Abstract:

[Background] Gut microbiota is closely related to the health and environmental adaptability of the host. Yak (Bos grunniens) is a herbivorous ruminant unique to the Qinghai-Tibet Plateau. The effect of altitude on the gut microbiota structure of yaks and the roles of gut microbiota in the adaption of yaks to high altitude, however, are still largely elusive. [Objective] This paper aims to explore the diversity of gut microbiota of yaks grazing on the Qinghai-Tibet Plateau and the relationship with altitude. [Methods] A total of 22 fresh fecal samples were collected from yaks in Maqin (altitude:4 220 m) and Ledu (altitude:2 745 m) of Qinghai, and the V3-V4 region of 16S rRNA gene was amplified with universal primers and then subjected to high-throughput sequencing and analysis. [Results] A total of 1 723 018 valid reads were obtained from the 22 samples, which were clustered into 1 113 operational taxonomic units (OTUs) based on 97% similarity. The OTUs belonged to 263 genera and 22 phyla. Firmicutes, Bacteroidetes, Ruminococcaceae_UCG-005, and Rikenellaceae_RC9_gut_group dominated the samples from the two regions, despite the significant difference in abundance. As the altitude elevated, the abundance of Firmicutes and Ruminococcaceae_UCG-005 significantly increased, while that of Bacteroidetes and Rikenellaceae_RC9_gut_group significantly decreased. As for the structure and difference of gut microbiota, gut microbiota structure of yaks was dramatically affected by altitude. In addition, PICRUSt2 analysis revealed that related metabolic pathways in gut microbiota such as energy metabolism, cofactor and vitamin metabolism, nucleotide metabolism, and glycan and amino acid metabolism were significantly enriched in yaks grazing at the higher altitude, in part because yaks improved forage utilization efficiency and harvested more energy to adapt to the extreme environment at higher altitude.[Conclusion] The gut microbiota structure of yak grazing at different altitudes was obviously different, and gut microbiota was proposed to play an essential role in the adaption of yaks to the environment at high altitude.