Evidence of cellulose metabolism by the giant panda gut microbiome

Abstract

The giant panda genome codes for all necessary enzymes associated with a carnivorous digestive system but lacks genes for enzymes needed to digest cellulose, the principal component of their bamboo diet. It has been posited that this iconic species must therefore possess microbial symbionts capable of metabolizing cellulose, but these symbionts have remained undetected. Here we examined 5,522 prokaryotic ribosomal RNA gene sequences in wild and captive giant panda fecal samples. We found lower species richness of the panda microbiome than of mammalian microbiomes for herbivores and nonherbivorous carnivores. We detected 13 operational taxonomic units closely related to Clostridium groups I and XIVa, both of which contain taxa known to digest cellulose. Seven of these 13 operational taxonomic units were unique to pandas compared with other mammals. Metagenomic analysis using ∼37-Mbp contig sequences from gut microbes recovered putative genes coding two cellulose-digesting enzymes and one hemicellulose-digesting enzyme, cellulase, β-glucosidase, and xylan 1,4-β-xylosidase, in Clostridium group I. Comparing glycoside hydrolase profiles of pandas with those of herbivores and omnivores, we found a moderate abundance of oligosaccharide-degrading enzymes for pandas (36%), close to that for humans (37%), and the lowest abundance of cellulases and endohemicellulases (2%), which may reflect low digestibility of cellulose and hemicellulose in the panda's unique bamboo diet. The presence of putative cellulose-digesting microbes, in combination with adaptations related to feeding, physiology, and morphology, show that giant pandas have evolved a number of traits to overcome the anatomical and physiological challenge of digesting a diet high in fibrous matter.

Whole-genome sequencing of the snub-nosed monkey provides insights into folivory and evolutionary history

“…Glycoside hydrolase genes were also identified, and over 929 genes and modules were recovered from 47 different CAZy families (carbohydrate active enzymes). Although there were not significant differences in the abundance of debranching enzymes in comparisons of the GSM, giant panda 22 , tammar 23 and termite 24 hindguts, there were considerably more GH78 sequences in GSM. As in giant panda, the abundance of cellulases and endohemicellulases in GSM was generally lower than in human, cattle and termite (Supplementary Table 34).…”

Functional diversity within the simple gut microbiota of the honey bee

“…The metagenome provides an initial picture of the functional capabilities of the bee gut microbiota. For an indication of what functions might be unusually prominent in the honey bee-associated community, compared with the gut microbiota of other animals, we compared the profile of Clusters of Orthologous Group (COG) functions to nine metagenomic datasets from the gut-associated microbial communities from five mammals and four insects (21)(22)(23)(24)(25)(26). We found a total of 72 COGs to be significantly enriched in the honey bee dataset in at least eight of the nine comparisons (SI Appendix, Table S2).…”

Assessing persistent organic pollutants (POPs) in the Sicily Island atmosphere, Mediterranean, using PUF disk passive air samplers

“…The estimated 1864 remaining giant pandas (State Forestry Administration of the People's Republic of China 2015) are facing many humaninduced threats including road construction, timber harvesting, and livestock grazing (Hull et al 2014;Hong et al 2015Hong et al , 2016Liu 2015;Zhang et al 2017a). Although pandas have a simple digestive tract with no enzymes to digest the cellulose that is found in fibrous bamboo culms (Hu et al 2010;Li et al 2010;Wei et al 2012;Nie et al 2015), they do have adaptations that allow them to subsist on a bamboo diet such as enlarged molars and specialized gut microbes to aid in cellulose digestion (Zhu et al 2011).…”