Adaptation to a bamboo diet is an essential process for giant panda growth, and gut microbes play an important role in the digestion of the polysaccharides in bamboo. The dietary transition in giant panda cubs is particularly complex, but it is an ideal period in which to study the effects of gut microbes on polysaccharide use because their main food changes from milk to bamboo (together with some bamboo shoot and coarse pastry). Here, we used 16S rDNA and internal transcribed spacer 1 (ITS1) DNA sequencing and metagenomic sequencing analysis to investigate the succession of the gut microbial structure in feces sampled from twin giant panda cubs during the completely dietary transition and determine the abundances of polysaccharide-metabolizing genes and their corresponding microbes to better understand the degradation of bamboo polysaccharides. Successive changes in the gut microbial diversity and structure were apparent in the growth of pandas during dietary shift process. Microbial diversity increased after the introduction of supplementary foods and then varied in a complex way for 1.5–2 years as bamboo and complex food components were introduced. They then stabilized after 2 years, when the cubs consumed a specialized bamboo diet. The microbes had more potential to metabolize the cellulose in bamboo than the hemicellulose, providing genes encoding cellulase systems corresponding to glycoside hydrolases (GHs; such as GH1, GH3, GH5, GH8, GH9, GH74, and GH94). The cellulose-metabolizing species (or genes) of gut bacteria was more abundant than that of gut fungi. Although cellulose-metabolizing species did not predominate in the gut bacterial community, microbial interactions allowed the giant pandas to achieve the necessary dietary shift and ultimately adapt to a bamboo diet.

适应竹子饮食是大熊猫生长的重要过程，肠道微生物在竹子多糖的消化中发挥着重要作用。大熊猫幼崽的饮食转变尤其复杂，但这是研究肠道微生物对多糖利用影响的理想时期，因为它们的主要食物从牛奶变为竹子（还有一些竹笋和粗糕点）。在这里，我们使用16S rDNA和内转录间隔区1（ITS1）DNA测序和宏基因组测序分析来研究双胞胎大熊猫幼崽在完全饮食转变期间粪便中肠道微生物结构的演替，并确定多糖代谢的丰度基因及其相应的微生物，以更好地了解竹多糖的降解。在饮食转变过程中，大熊猫的生长过程中肠道微生物多样性和结构发生了明显的连续变化。引入补充食品后，微生物多样性有所增加，然后随着竹子和复杂食品成分的引入，微生物多样性在 1.5-2 年内以复杂的方式发生变化。两年后，当幼崽食用专门的竹子食物时，它们的情况就稳定下来了。与半纤维素相比，微生物更有潜力代谢竹子中的纤维素，提供编码与糖苷水解酶（GH；例如 GH1、GH3、GH5、GH8、GH9、GH74 和 GH94）相对应的纤维素酶系统的基因。肠道细菌的纤维素代谢物种（或基因）比肠道真菌更丰富。 尽管纤维素代谢物种在肠道细菌群落中并不占主导地位，但微生物相互作用使大熊猫实现了必要的饮食转变并最终适应了竹子饮食。