大熊猫的肠道细菌不能有效地消化竹子

It's no wonder that giant pandas are always chewing and eating, say Chinese researchers: their gut¹ bacteria are not the type for efficiently² digesting bamboo. The bamboo-eating giant panda actually harbors a carnivore-like gut microbiota predominated by bacteria such as Escherichia/Shigella and Streptococcus, according to new research published this week in mBio®, the online open-access journal of the American Society for Microbiology.   "Unlike other plant-eating animals that have successfully evolved, anatomically specialized³ digestive systems to efficiently deconstruct fibrous plant matter, the giant panda still retains a gastrointestinal tract⁴ typical of carnivores," said lead study author Zhihe Zhang, director of the Chengdu Research Base of Giant Panda Breeding, China. "The animals also do not have the genes⁵ for plant-digesting enzymes⁶ in their own genome. This combined scenario⁷ may have increased their risk for extinction⁸."   "This result is unexpected and quite interesting, because it implies the giant panda's gut microbiota may not have well adapted to its unique diet, and places pandas at an evolutionary⁹ dilemma," said study coauthor Xiaoyan Pang¹⁰, PhD, MSc, an associate professor in the School of Life Sciences and Biotechnology at Shanghai Jiao Tong University.   Giant pandas evolved from bears that ate both plants and meat, researchers said, and started eating bamboo exclusively about two million years ago. The animals spend up to 14 hours daily consuming up to 12.5 kg (27.5 pounds) of bamboo leaves and stems but can digest only about 17 percent of it; their feces is mainly composed of undigested bamboo fragments. Researchers had been intrigued¹¹ by how the animals digest bamboo fiber¹² and extract nutrients¹³ from it, Pang said.