How gut bacteria help pandas eat only bamboo and maintain weight

Pandas are notoriously picky about food. They only consume bamboo – a low-quality, low-fat diet.

But these animals appear to have evolved to get the most out of what they eat, according to a new study.

The panda’s gut bacteria change in late spring and early summer, when bamboo is most nutritious — while sprouting green, protein-rich shoots. The bacteria make the bear gain more weight and store more fat, which the researchers say can make up for a lack of nutrients later in the year, when bamboo plants have only fibrous leaves to chew on.

“We’ve known for a long time that these pandas have a different set of gut flora during the bud-feeding season, and it’s very obvious that they are chubby during this time of year,” said study lead author Guangping Huang, researcher. from the Institute of Zoology of the Chinese Academy of Sciences in a press release.

The study was published Tuesday in the scientific journal Cell Reports.

To investigate how gut bacteria might affect a panda’s metabolism, the team first collected the feces of eight wild giant pandas in China’s Qingling Mountains during the fibrous leaf and bud season, and then examined how the samples of these stools differed.

Scientists found that a bacillus called Clostridium butyricum was most abundant in pandas’ innards during the season when they enjoy fresh bamboo shoots.

To understand whether this bacterium helps bears gain and store weight, the researchers performed a fecal transplant, placing the feces collected from the pandas in laboratory mice. They then fed these mice for three weeks a bamboo-based diet that simulated what pandas eat.

Although mice are very different from pandas, it was not possible to perform these tests on vulnerable and endangered animals, said Wei Fuwen, co-author of the study and professor at the Key Lab of Animal Ecology and Conservation Biology at the Institute of Zoology of the Chinese Academy of Sciences. . Rats were a good substitute.

“Mice proved to be an effective model for studying gut microbiome function in humans,” Wei said by email.

The researchers found that mice transplanted with panda feces collected during the bud-feeding season gained significantly more weight despite consuming the same amount of food.

“Gut bacteria was the only variable in this research,” explained Wei.

Felix Sommer, leader of the host microbiome functional research group at Christian-Albrechts University in Kiel, Germany, noted that the number of pandas involved in the study was small and the experiment had only been carried out once. Sommer, who was not involved in the research, also emphasized that the researchers found a correlation, not a causal relationship, between the bacteria and weight gain.

“I would have asked for some sort of validation experiment or re-sampling in another year or another time,” explained Sommer, who has conducted similar research on brown bear hibernation.

Wei said more work is needed to validate the causal relationship directly in pandas. He added that their work could help improve the health of giant pandas kept in captivity.