Table9.PDF

Bamboo-eating giant panda (Ailuropoda melanoleuca) is an enigmatic species, which possesses a carnivore-like short and simple gastrointestinal tract (GIT). Despite the remarkable studies on giant panda, its diet adaptability status continues to be a matter of debate. To resolve this puzzle, we investigated the functional potential of the giant panda gut microbiome using shotgun metagenomic sequencing of fecal samples. We also compared our data with similar data from other animal species representing herbivores, carnivores, and omnivores from current and earlier studies. We found that the giant panda hosts a bear-like gut microbiota distinct from those of herbivores indicated by the metabolic potential of the microbiome in the gut of giant pandas and other mammals. Furthermore, the relative abundance of genes involved in cellulose- and hemicellulose-digestion, and enrichment of enzymes associated with pathways of amino acid degradation and biosynthetic reactions in giant pandas echoed a carnivore-like microbiome. Most significantly, the enzyme assay of the giant panda's feces indicated the lowest cellulase and xylanase activity among major herbivores, shown by an in-vitro experimental assay of enzyme activity for cellulose and hemicellulose-degradation. All of our results consistently indicate that the giant panda is not specialized to digest cellulose and hemicellulose from its bamboo diet, making the giant panda a good mammalian model to study the unusual link between the gut microbiome and diet. The increased food intake of the giant pandas might be a strategy to compensate for the gut microbiome functions, highlighting a strong need of conservation of the native bamboo forest both in high- and low-altitude ranges to meet the great demand of bamboo diet of giant pandas.

竹食性大熊猫（Ailuropoda melanoleuca）是一种神秘物种，其具有类似肉食动物之短而简单的消化系统（GIT）。尽管对大熊猫的研究成果丰硕，但其饮食适应性状态仍旧是争议的焦点。为解开这一谜团，我们通过粪便样本的散弋宏基因组测序技术，研究了大熊猫肠道微生物组的机能潜力。同时，我们将我们的数据与现有及早期研究中来自代表食草动物、肉食动物和杂食动物的其它动物物种的类似数据进行了比较。我们发现，大熊猫拥有类似熊类的肠道微生物群，与食草动物的微生物群存在显著差异，这一差异可通过大熊猫及其他哺乳动物肠道微生物群的代谢潜力得到体现。此外，大熊猫肠道中参与纤维素和半纤维素降解的基因相对丰度，以及与氨基酸降解和生物合成途径相关的酶的富集，均反映出类似肉食动物的微生物群特征。尤为显著的是，大熊猫粪便的酶活性分析表明，其在主要食草动物中纤维素酶和木聚糖酶活性最低，这一结果通过体外酶活性实验得到了验证。所有这些结果均一致表明，大熊猫并未特化为消化其竹子饮食中的纤维素和半纤维素，从而使其成为研究肠道微生物群与饮食之间异常联系的理想哺乳动物模型。大熊猫食物摄入量的增加可能是为了补偿肠道微生物群的功能，凸显了在高海拔和低海拔地区保护原生竹林的重要性，以满足大熊猫对竹子饮食的巨大需求。