Bamboo, bamboo and more bamboo. That’s what pandas eat. However, the bears’ gut microbiome is very well adapted to this diet. It even changes its composition depending on the season in order to draw the most energy from the plant diet, as a team led by zoologist Guangping Huang from the Chinese Academy of Sciences reports in the journal Cell Reports. The bears’ intestinal flora ensures that they can accumulate sufficient fat when they mainly eat bamboo shoots in spring.
Because the animals are under protection, Huang and his team did not carry out their experiments on pandas themselves, but used the microbiome of germ-free mice. To do this, they collected samples of panda excrement and thus gave the test animals the intestinal flora that bears have in spring and that which they carry in their digestive tract at other times of the year. The mice were then fed bamboo for three weeks. It was shown that the animals with the spring microbiome gained more weight than the other mice, although all animals consumed the same amount of food.
In the spring, a certain type of microbe predominates in the pandas’ guts: Clostridium butyricum. It ensures that the animals get more energy from this form of food at this time of year when the protein-rich bamboo shoots are growing. In the spring, the pandas can eat bacon. In the rest of the year, they feed mainly on bamboo leaves, which are less nutrient-rich. Using the mice, the researchers were able to demonstrate at the molecular level that Clostridium butyricum influences the fat metabolism of the animals and ensures the storage of lipids.
The phenomenon of a seasonally changing microbiome has also been documented in humans. In the Hadza, who live as hunters and gatherers in Tanzania, the intestinal flora changes depending on the season, as a working group demonstrated in 2017.