A specific strain of bacteria living in the gut appears to prompt mother mice to neglect their pups, as shown by a new study in the journal Science Advances. The study was only carried out on mice, but the research could shed some light on the wider understanding of how the gut microbiome can have a profound effect on brain health, mood, and behavior.
“To our knowledge, this is the first demonstration that the intestinal microbiota is important for promoting healthy maternal behavior and bonding between mom and offspring in an animal model,” Professor Janelle Ayres, senior study author and Laboratory Head of Salk’s Molecular and Systems Physiology Laboratory, said in a statement.
“It adds to the ever-growing evidence that there’s a gut-brain connection, and that microbes are important for regulating the behavior of the host that they’re inhabiting.”
The bacteria in question is one particular strain of the common bacteria E. coli, known as O16:H48 MG1655. The researchers noted that mice with this strain of bacteria in their gut tended to mother offspring that had stunted growth, so they investigated why. However, their initial probing didn’t find anything too unusual; the baby mice were behaving normally and the mothers’ milk was perfectly nutritious. Eventually, they realized there was a link between the presence of the bacterial strain and the mothers’ behavior, specifically in regards to how much she cared for her offspring.
To rule out any other possible factors, the team gave the malnourished mice a growth factor or handed them off to “foster mouse mothers”, helping to prove that the stunted growth was caused by the mothers’ behavior.
It’s tricky to say how these findings can be applied to humans since our behavior is immensely more complex than mouse behavior. The O16:H48 MG1655 strain of E. coli has been found in human guts, but it was previously believed to have neither positive nor negative effects. Nevertheless, science’s understanding of the gut microbiome has dramatically increased in recent years with a huge number of recent studies starting to uncover the mysterious link between our brains and the microorganisms that live in our guts.
One of the most intriguing insights is how a person’s make-up on gut bacteria may have some impact on their mental health or brain health. A study from 2019 found that two groups of bacteria, Coprococcus and Dialister, were depleted in people suffering from depression. Other recent studies have even found clear links between the gut microbiome and Alzheimer's disease.
“It’s very hard to study these relationships in humans, because the human microbiota contains hundreds of different species of microorganisms,” adds Professor Ayres. “But once we understand more about the mechanisms in animal models, we may be able [to] translate our findings to humans to determine whether the microbes and their effects might be the same."
