Bacterial biogeography of pika gastrointestinal tract

The mammalian microbiota in the gastrointestinal tract (GIT) play important roles in host nutrition and health, while few studies has investigated microbial diversity, interactions and community stability across the GIT in wild mammals. Using 16S rRNA gene sequencing, we analyzed the bacterial diversity, network interactions and ecosystem stability across five gut chambers (mouth, stomach, small intestine, caecum and colon) from two common pika (Ochotona spp.) species in China, including Plateau pikas (O. curzoniae) from high-altitude regions and Daurian pikas(O. daurica) from low-altitude areas. The relative abundances of dominant Firmicutes and Bacteroidetes had an increasing trend from mouth to colon. Caecum and colon harbored higher bacterial diversity compared with other anatomical regions. Gut region significantly influenced the structure of bacterial communities in the GIT. Notably, the mouth or stomach community structure was highly similar between Plateau pikas and Daurian pikas, while the bacterial communities from small intestine, caecum or colon showed significant differences between host species. The cecal bacterial community of Plateau pikas was more conserved than that of Daurian pikas. Network analysis indicated that topological features showed marked variations among gut regions or between host species. Interestingly, the ecosystem stability of bacterial communities decreased gradually from mouth to colon. Our results suggested that gut region and host species influence the diversity, structure, and network interactions of bacterial communities in pika digestive tract. For hindgut-fermenting mammals, relatively higher bacterial diversity and ecosystem stability in the caecum may provide a favorable condition for the fermentation of plant polysaccharides.

胃肠道（gastrointestinal tract, GIT）内的哺乳动物微生物群在宿主营养与健康中发挥重要作用，但目前针对野生哺乳动物胃肠道全区段的微生物多样性、物种互作及群落稳定性的研究仍较为匮乏。本研究通过16S rRNA基因（16S rRNA gene）测序技术，对中国境内两种常见鼠兔属（Ochotona spp.）动物的五个肠道区段——口腔、胃、小肠、盲肠及结肠的细菌多样性、网络互作与生态系统稳定性展开分析。两种鼠兔分别为来自高海拔区域的高原鼠兔（O. curzoniae）与低海拔区域的达乌尔鼠兔（O. daurica）。优势菌门厚壁菌门（Firmicutes）与拟杆菌门（Bacteroidetes）的相对丰度自口腔至结肠呈逐步上升趋势。盲肠与结肠的细菌多样性显著高于其余解剖区段。肠道区段显著影响胃肠道内细菌群落的组成结构。值得注意的是，高原鼠兔与达乌尔鼠兔的口腔或胃部细菌群落结构高度相似，而二者小肠、盲肠或结肠的细菌群落则在宿主物种间存在显著差异。高原鼠兔的盲肠细菌群落相较于达乌尔鼠兔更为保守。网络分析结果显示，不同肠道区段以及不同宿主物种间的细菌群落拓扑特征存在显著差异。有趣的是，细菌群落的生态系统稳定性自口腔至结肠呈逐步降低趋势。本研究结果表明，肠道区段与宿主物种共同影响鼠兔消化道内细菌群落的多样性、组成结构及网络互作模式。对于后肠发酵型哺乳动物而言，盲肠内相对较高的细菌多样性与生态系统稳定性或为植物多糖发酵提供了有利条件。