The human gut microbiota with reference to autism spectrum disorder: considering the whole as more than a sum of its parts

Abstract

The human gut microbiota is a complex microbial ecosystem that contributes an important component towards the health of its host. This highly complex ecosystem has been underestimated in its importance until recently, when a realization of the enormous scope of gut microbiota function has been (and continues to be) revealed. One of the more striking of these discoveries is the finding that the gut microbiota and the brain are connected, and thus there is potential for the microbiota in the gut to influence behavior and mental health. In this short review, we outline the link between brain and gut microbiota and urge the reader to consider the gut microbiota as an ecosystem 'organ' rather than just as a collection of microbes filling a niche, using the hypothesized role of the gut microbiota in autism spectrum disorder to illustrate the concept.

Keywords: Autism Spectrum Disorder; gastrointestinal tract; human; microbiota.

Fig. 1

Trends in human microbiome research over the last decade: PubMed Citations by year using search term ‘Human microbiome’. Y-axis: number of publications.

Fig. 2

Pictorial representation of the routes for, and blockages of, microbial colonization of Westernized humans during early life. On the left of the figure, routes of natural colonization are depicted, while on the right, impediments to natural colonization are shown.