Human Intestinal Microbial Ecology and its Relationship to Autism

Unusually high proportions of autistic children suffer from gastrointestinal problems, suggesting a link between autism and abnormalities in gut microbial function. Disturbances in gut microbial ecosystems not only cause gastrointestinal problems that can exacerbate autistic symptoms, but may also affect the immune and neurological systems. Previous studies have focused primarily on the autism-related presence of pathogenic bacteria. Hence, we investigated autism-related alteration of intestinal bacterial composition by comparing non-autistic and autistic children with or without gastrointestinal symptoms. Interestingly, autistic children tend to have less diverse bacterial communities in their intestines, regardless of noticeable gastrointestinal symptoms. In addition, extensive bioinformatics and statistical analyses discovered that the genus Prevotella was mostly absent in autistic children, which in contrast was found in a large fraction of non-autistic children. Intriguingly, these microbes are known to function as a primary degrader of polysaccharides in gut, suggesting a possible influence of daily diets. In addition, Prevotella was recently reported as a central component of gut microbial communities in humans. Therefore, our findings suggest that the less diverse and imbalanced gut microbial profiles of autistic children make them more susceptible to frequent gastrointestinal disorders.