Gut bacteria may contribute directly to the development of autism-like behaviors, according to the results of a new study in mice.
In their study, which features in the journal Cell, researchers from the California Institute of Technology (Caltech) in Pasadena built on the work of previous studies that identified differences in the microbiomes of people with and without autism spectrum disorder (ASD).
The microbiome is the name for the collective genomes belonging to the communities of microorganisms that inhabit the human gut.
"In recent years, numerous studies have revealed differences in the bacterial composition of the gut microbiome between individuals with ASD and neurotypical [people]," says author Sarkis Mazmanian.
"However, while this previous research identifies potentially important associations, it is unable to resolve whether observed microbiome changes are a consequence of having ASD or if they contribute to symptoms."
The Centers for Disease Control and Prevention (CDC) report that about one in 59 children in the United States have received a diagnosis of ASD, which is about four times more common in boys than girls and occurs across all socioeconomic, ethnic, and racial groups.
Autistic people are prone to repetitive behavior and may sometimes face difficulties communicating. Scientists do not know exactly what causes ASD, but they believe that both genetic and environmental factors play a role.
'Autism' behavior in ASD microbiome mice
In their study, the Caltech researchers used laboratory mice that they had bred to lack a microbiome. They transplanted bacteria from the guts of children with ASD into one group of these "germ-free" mice.
To create a control group, the team transplanted gut bacteria from people without autism into another group of germ-free mice.
So, what happened? The Caltech team found that the mice with transplanted microorganisms from children with ASD began to exhibit behaviors similar to those that are characteristic of autism in humans.