Abstract
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.
Highlights
The giant panda, Ailuropoda melanoleuca, is the flagship species of biodiversity conservation throughout the world (Wei et al, 2019)
To investigate the succession of intestinal microbes in giant panda cubs during dietary change and their adaptation to a bamboo diet, two captive-born giant pandas bred in the Shanghai Wild Animal Park and born in October 2016 were included in the study (Supplementary Table S1)
We characterized the fecal bacterial diversity of captive twin giant panda cubs raised at the Shanghai Wild Animal Park (Shanghai, China)
Summary
The giant panda, Ailuropoda melanoleuca, is the flagship species of biodiversity conservation throughout the world (Wei et al, 2019) It belongs to the order Carnivora and has a typical carnivorous intestinal structure (Zhang et al, 2007). Several microbial strains and GH genes that can degrade cellulose have been identified with high-throughput sequencing and culture in vitro (Anand et al, 2012; Mearls and Lynd, 2014; Wang et al, 2016; Guo W. et al, 2018; Liu et al, 2019) These findings demonstrate, to some extent, the important status of cellulose in the nutrient usage of the giant panda. Hemicellulose is usually more stable than cellulose and harder to degrade (Bhat et al, 2011; Zhang et al, 2018)
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