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Exposure to psychological stress in the form of social conflict alters gut bacteria in Syrian hamsters, according to a new study by Georgia State University. It has been shown that gut microbiota, the complex community of microorganisms that live in the digestive tracts of humans and other animals, can send signals to the brain and vice versa.
Stress can alter the gut microbiota. The most common stress experienced by humans and other animals is social stress, and this stress worsen mental illness in humans. Researchers at Georgia State have examined whether mild social stress alters the gut microbiota in Syrian hamsters, and if so, whether this response is different in animals that “win” compared to those that “lose” in conflict situations.
Hamsters are ideal to study social stress because they rapidly form dominance hierarchies when paired with other animals. In this study, researchers placed pairs of adult males together and they quickly began to compete, resulting in dominant and subordinate animals that maintained this status throughout the experiment. Their gut microbes were sampled before and after the first encounter as well as after nine interactions.
Sampling was also done in a control group of hamsters that were never paired and thus had no social stress, they discovered that single exposure to social stress causes a change in the gut microbiota, similar to what is seen following other severe physical stressors, and this change gets bigger following repeated exposures. Social stress led to similar overall changes in the microbiota, although the particular bacteria that were impacted were somewhat different in winners and losers. It might be that the impact of social stress was somewhat greater for the subordinate animals.
Another unique finding came from samples that were taken before the animals were ever paired, which were used to determine if any of the preexisting bacteria seemed to correlate with whether an animal turned out to be the winner or loser. There were some bacteria that seemed to predict whether an animal would become a winner or a loser. Bi-directional communication is occurring with stress impacting the microbiota, and on the other hand, with some specific bacteria in turn impacting the response to stress.
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