Specific bacteria in the gut cause mother mice to neglect their young

As scientists learn more about the microorganisms that colonize the body – collectively called microbiota – an area of ​​intense interest is the effect these microbes can have on the brain. A new study by scientists at the Salk Institute has identified a strain of E. coli bacteria which, when living in the guts of female mice, cause them to neglect their offspring.

The results, published on January 29, 2021 in the journal Scientific advances, show a direct link between a particular microbe and maternal behavior. Although the research has been conducted in mice, it adds to the growing body of science demonstrating that microbes in the gut are important for brain health and can affect development and behavior.

“To our knowledge, this is the first demonstration that the gut microbiota is important for promoting healthy maternal behavior and links between mother and offspring in an animal model,” says Professor Janelle Ayres, head of laboratory at the Molecular Physiology and Salk Systems laboratory and lead author of the paper. “This adds to the growing evidence that there is a gut-brain connection and that microbes are important in regulating the behavior of the host they inhabit.

How the microbiota can impact mental health and neurological disorders is a growing area of ​​research. The makeup of the gut microbiota in people has been linked to depression, anxiety, autism, and other conditions. But it has been difficult to study how individual strains of bacteria exert their influence on human behavior, a connection often referred to as the microbiota-gut-brain axis.

In his lab, Ayres uses mice to study how body systems and the brain interact with each other to promote health. This includes focusing on how bodily processes are regulated by microbes and how microbes affect growth and behavior. In current experiments, she and her team were investigating groups of mice that each had a single strain of E. coli in their guts. Mice with a particular strain of E. coli, called O16: H48 MG1655, mother offspring who were stunted. A closer examination revealed that the mice were smaller because they suffered from malnutrition.

“We found that the behavior of the puppies was normal and that the milk produced by the mothers was of normal and healthy composition and was produced in normal amounts,” says Ayres. “We finally figured out that colonization by this particular bacterium resulted in poor maternal behavior. Mice neglected their young.”

Further experiments revealed that mice could be saved from stunted growth, either by giving them a growth factor called IGF-1, or by transferring them to mothers of mice who could take care of them properly. This confirmed that the cause of the stunted growth was from the behavior of the mothers rather than something in the puppies themselves.

“Our study provides an unprecedented understanding of how the gut microbiota can disrupt maternal behavior and how this can negatively impact the development of offspring,” says first author Yujung Michelle Lee, former graduate student of the lab d’Ayres and now a postdoctoral researcher at Genentech. . “It’s very interesting to me that building a healthy mother-child relationship is driven by factors beyond hormones, and that the microorganisms residing in our bodies play an important role in it.”

Ayres and his team plan to study how these microbes cause changes in the behavior of mice. Early findings suggest the bacteria may affect levels of serotonin, the hormone associated with feelings of happiness and well-being, but more effort is needed.

“It is very difficult to study these relationships in humans because the human microbiota contains hundreds of different species of microorganisms,” says Ayres, who holds the Helen McLoraine Chair in Development. “But once we know more about the mechanics of animal models, we may be able to translate our findings to humans to determine if the microbes and their effects might be the same.”

The O16: H48 strain MG1655 has been found in the human intestines and was previously thought to have no positive or negative effects.