CONCLUSIONS
Overall, these data strongly indicate that diets and lifestyles are associated with the richness, diversity, and compositions of the GM of giant pandas. Specifically, the GM of giant pandas was more similar when the hosts exhibited the same diet or lifestyle. High fiber diets significantly increased the diversity, while decreasing the richness of gut bacterial populations of giant pandas (p < 0.05). In addition, the abundances of Streptococcus , Pseudomonas ,Enterococcus, Lactococcus, Acinetobacter, andClostridium significantly increased with bamboo consumption. Reconstruction of 22 metagenome-assembled-genomes (MAGs) indicated that gut bacterial populations were potentially responsible for bamboo digestion via degradation of cellulose, hemicellulose, and lignin. Captivity resulted in decreased GM diversity, especially of fungi, in the pandas. Specifically, gut bacterial community richness and diversity in wild giant pandas were significantly higher than in those of wild-training I or wild-training II pandas (p < 0.05). Likewise, fungal community richness and diversity of reintroduced and wild giant pandas were significantly higher than in those of wild-training I and wild-training II pandas (p < 0.05). Notably, the composition of GM in reintroduced giant pandas converged to those of wild pandas. Food choices and environmental meta-communities could therefore drive the structure of giant panda gut microbiomes. Further, we suggest that adaptation to increasing environmental threats or stressors could help converge the GM compositions of giant pandas to those of wild pandas.
Acknowledgements
We thank Yu Zhou, Wen Zeng and Min He for help with the sample and data collection.