Scoma Alberto, Khor Way Cern, Coma Marta, Heyer Robert, Props Ruben, Schoelynck Jonas, Bouts Tim, Benndorf Dirk, Li Desheng, Zhang Hemin, Rabaey Korneel
Center for Microbial Ecology and Technology, University of Ghent, Ghent, Belgium.
Department of Bioscience, Microbiology Section, Aarhus University, Aarhus C, Denmark.
Front Microbiol. 2020 Mar 31;11:530. doi: 10.3389/fmicb.2020.00530. eCollection 2020.
The giant panda is known worldwide for having successfully moved to a diet almost exclusively based on bamboo. Provided that no lignocellulose-degrading enzyme was detected in panda's genome, bamboo digestion is believed to depend on its gut microbiome. However, pandas retain the digestive system of a carnivore, with retention times of maximum 12 h. Cultivation of their unique gut microbiome under controlled laboratory conditions may be a valid tool to understand giant pandas' dietary habits, and provide valuable insights about what component of lignocellulose may be metabolized. Here, we collected gut microbiomes from fresh fecal samples of a giant panda (either entirely green or yellow stools) and supplied them with green leaves or yellow pith (i.e., the peeled stem). Microbial community composition was substrate dependent, and resulted in markedly different fermentation profiles, with yellow pith fermented to lactate and green leaves to lactate, acetate and ethanol, the latter to strikingly high concentrations (∼3%, v:v, within 3.5 h). Microbial metaproteins pointed to hemicellulose rather than cellulose degradation. The alpha-amylase from the giant panda (E.C. 3.2.1.1) was the predominant identified metaprotein, particularly in reactors inoculated with pellets derived from fecal samples (up to 60%). Gut microbiomes assemblage was most prominently impacted by the change in substrate (either leaf or pith). Removal of soluble organics from inocula to force lignocellulose degradation significantly enriched (in green leaf) and / (in yellow pith). Overall, different substrates (either leaf or pith) markedly shaped gut microbiome assemblies and fermentation profiles. The biochemical profile of fermentation products may be an underestimated factor contributing to explain the peculiar dietary behavior of giant pandas, and should be implemented in large scale studies together with short-term lab-scale cultivation of gut microbiomes.
大熊猫因成功转向几乎完全以竹子为食的饮食习惯而闻名于世。鉴于在大熊猫基因组中未检测到木质纤维素降解酶，人们认为竹子的消化依赖于其肠道微生物群。然而，大熊猫保留了食肉动物的消化系统，食物在其体内的停留时间最长为12小时。在可控的实验室条件下培养它们独特的肠道微生物群，可能是了解大熊猫饮食习惯的有效工具，并能为木质纤维素的哪些成分可能被代谢提供有价值的见解。在这里，我们从一只大熊猫的新鲜粪便样本（绿色或黄色粪便）中收集肠道微生物群，并为它们提供绿叶或黄色髓心（即去皮茎）。微生物群落组成取决于底物，并导致明显不同的发酵谱，黄色髓心发酵生成乳酸，绿叶发酵生成乳酸、乙酸和乙醇，后者在3.5小时内浓度显著升高（约3%，v:v）。微生物元蛋白质表明是半纤维素而非纤维素被降解。大熊猫的α-淀粉酶（E.C. 3.2.1.1）是鉴定出的主要元蛋白质，特别是在接种粪便样本颗粒的反应器中（高达60%）。肠道微生物群的组装受底物（叶或髓心）变化的影响最为显著。从接种物中去除可溶性有机物以促使木质纤维素降解，显著富集了（在绿叶中）和 / （在黄色髓心中）。总体而言，不同的底物（叶或髓心）显著塑造了肠道微生物群的组装和发酵谱。发酵产物的生化谱可能是一个被低估的因素，有助于解释大熊猫独特的饮食行为，应在大规模研究中与肠道微生物群的短期实验室规模培养一起实施。
