The giant panda (Ailuropoda melanoleuca) is a highly vulnerable mammal (The IUCN Red List of Threatened Species, 2016), whilst being the most iconic and flagship species for wildlife conservation worldwide.The giant panda, a member of family Ursidae and possessing a typical carnivore like short gastrointestinal tract, is an enigmatic species because it consumes nearly 12.5 kg of highly fibrous bamboo leaves and stems each day, and it became full-time bamboo eating species by the late Pliocene (2 Mya).Along with the threat of climate change, this bamboo specialist is at risk to extinction because of its sole reliance on large quantities of low-nutrition and low-energy content food from bamboo.The profound investigation of Pandas genome has reported that it encodes all enzymes crucial for a carnivorous digestive system but lacks those required for digesting cellulose rich bamboo diet.Despite the excellent studies on Tas1r1 pseudogenization (umami taste receptor gene) and appetite-reward system in the pandas genome to understand the evolutionary consequences of dietary switch of the panda, there is still uncertainty about the underlying mechanisms and one question still remains unanswered;"why pandas shifted to bamboo diet?" Under such circumstances, it was believed that the giant panda is dependent on gut microbiota in order to adapt to highly fibrous bamboo diet.While, gastrointestinal disease is reported to be a primary cause of death in both wild and captive.Therefore, it becomes most significant to understand, how gut microbiota impacts pandas health and nutrition, and biology behind this mechanism.Recent metagenomic study found the Clostridiura bacteria in giant panda gut contains genes known to code enzymes that digest cellulose (Zhu et al., 2011), which was opposed later by a current study with larger sample size of captive pandas which suggested that pandas carnivore-like gut microbiota has not evolved to efficiently digest cellulose from a fibre-rich bamboo diet (Xue et al.2015).In contrast, few genomic biologists believed that the pandas shift to a bamboo diet millions of years ago, might have led to a shift in composition and function of gut microbiota, which still retains few microbes that might be capable of digesting cellulose and it is hard to conclude anything if the research is based on just microbial composition, not the function.Thus, we investigated the structural profile and functional potential of the giant panda gut microbiome comprehensively using 16S rRNA and shotgun metagenomic sequencing of fecal samples and presented direct evidence of cellulose-and hemicelluloses-digestion by gut microbiota of the giant panda in order to provide a comprehensive understanding on this dilemma.Our results of 16S community composition are similar to the recent study on captive giant pandas (Xue et al.2015)which presents the confident dataset for the comprehensive assessment of gut microbiota of wild giant panda with the largest number of samples till date.Metagenomic functional potential profile (including all KEGG pathways and pathways involved in carbohydrate, amino acids, energy and lipid metabolism) of the giant panda echoes a carnivore like microbiome and distinct from those of herbivores.We found that cellulose-and hemicellulose-degradation pathways and associated genes are present in all animal groups (including herbivore, carnivores, and omnivores) along with giant panda.Therefore, we urge that based on just the presence of cellulose degradation pathway, it is hard to conclude about pandas diet adaptability.To establish such assumptions, we evaluated the abundance of genes involved in these pathways and found that their relative abundances in giant panda were similar to carnivores and lower than those of herbivores.To present the direct evidence, a comparative cellulose-degradation activity profile indicated that the giant panda showed a very low-level enzyme-activity like bears as compared to higher enzyme-activity in herbivores.Therefore, this finding clearly indicates that giant panda cannot efficiently digest cellulose and hemicellulose like herbivores.Furthermore, the glutamate and pyruvate metabolism pathways clearly indicated that the bamboo-eating giant panda does not retain genes to degrade plant-based diet.Moreover, the distribution of CAZy families in the gut of giant panda revealed that giant panda harbor more similar CAZy families like carnivores than those of herbivore.Here we prove that the ability of the pandas microbiota to digest cellulose is very poor, so the simple gut and the poor efficiency to utilize the cellulose seem to affect the food habits.Our results supported that the evolution of gut microbiota in the giant panda was consistent with the phylogeny of the host.